LINE Sticker AI Prompts: Keep Your Character Consistent

Ask an AI to "draw a cute dog sticker" and the first image comes out surprisingly adorable. The trouble starts on the second one. You asked for the same thing, but the color shifts, the face changes, and before long it's a different dog entirely. A LINE sticker set needs up to 40 stickers of the same character, so this "character drift" is the single biggest obstacle.

This article walks through how to write LINE sticker prompts with one question in mind —how do you keep the character from drifting — covering the basic structure, how to generate variations, and the spec details that trip people up.

The basic structure of a LINE sticker prompt

Just saying "make it cute" forces the AI to reinterpret everything from scratch every time — no wonder the results are inconsistent. A LINE sticker prompt gets much more predictable once you cover these six elements:

• Who: the character type and key traits (e.g., a chibi white puppy)
• What: the pose or action (e.g., both arms raised, overjoyed)
• Linework and color: line weight/style and the base palette (e.g., soft, even-weight lines, a 3-color palette)
• Expression: specifics down to the eyes and mouth (e.g., eyes closed, beaming smile)
• Margin: the whole body fits inside the frame with space around it
• Background: transparent, or a flat color that's easy to key out later

Put together, it looks something like this:

Here's the thing: longer isn't better. Piling on adjectives helps less than listing a handful of unambiguous specs in the same order every time. And rather than pointing at a style with "in the style of ___," describe the style in terms of its parts — line weight, color count, brush texture.

Locking down the parameters that keep 40 stickers on-model

For a single sticker, the template above is enough. So what happens at 40? You end up rephrasing things slightly every time, and that wording drift becomes character drift. That's exactly why it pays to lock down a "blueprint" before you start generating.

Fix the eyes, mouth, outline, and palette first

Start by picking one image you like as your "reference," then put its look into words. There are four things to nail down:

• Eyes: shape (round, droopy, upturned), size, whether there's a highlight
• Mouth: size, default shape (smile, flat line, small dot)
• Outline: face and body silhouette (round face, two-head-tall proportions, short limbs)
• Palette: narrow it down to 2–3 named colors (e.g., white, cream, pale blue)

Fold those four points into a single block of text, then copy and reuse that exact block for every sticker, only swapping the pose and expression that follow it. The moment you rely on memory — "how did I phrase it yesterday?" — is the moment drift creeps in, so save the fixed block somewhere like a notes app. If your tool lets you attach a reference image, adding the same reference every time locks things down even further.

Leave out specific franchise or brand names

Writing "make it look like [some famous character]" is a genuine shortcut to a certain vibe — but avoid it. The issue isn't quality, it's rights. A result that resembles a specific franchise or brand can get rejected during LINE's review, or cause problems after you've put it up for sale.

Instead, break the vibe you're after into components — "big eyes," "rounded silhouette," "soft color palette." It takes a little more effort to communicate, but what comes out is a character that's genuinely yours, rights and all. For more on review and AI-disclosure rules, see our guide to AI sticker rules and disclosure requirements.

A framework for generating expression and phrase variations

Once the character is locked, the next question is: what do you actually put on 40 stickers? This is where an emotion map helps. Put everyday greetings and replies along one axis and a range of emotions along the other, then multiply the two together. Even the same "thank you" becomes a completely different sticker once you change the emotion behind it.

Three phrases times four emotions already gets you twelve ideas. Add in "good morning," "good night," "sorry," and "leave it to me," and 40 stickers fill up faster than you'd expect. As a rough split, aim for about half greetings-and-replies, half emotional reactions. If you're stuck, picture one specific person you'd actually send this sticker set to, and pick phrases from the words you use most with them — you won't go wrong.

Where people get stuck: size, margin, and transparency

Even once the art is done, LINE's spec is its own hurdle. Here are three sticking points that prompting alone won't solve.

• Size: sticker images need to be 370×320px, with both width and height as even numbers. Most image-generation AI can't hit an exact pixel count on request, though, so it's more realistic to generate oversized and plan to resize yourself afterward.
• Margin: you need roughly 10px of space around the character. Skip phrases like "whole body fits in the frame" or "leave margin around the subject," and heads and ears tend to get cropped off.
• Transparency: submissions need to be a PNG with a transparent background. Some tools can't output true transparency and instead draw a checkerboard pattern into the image itself to fake it — watch out for that. It's safer to generate against a flat-color background and handle transparency as a separate step.

For the official spec, check the LINE Creators Market sticker guidelines (official). We've also written up the full LINE sticker submission guide.

Or skip writing prompts altogether

Be honest — how does all this sound so far? If your reaction is "building a template sounds fun, but managing 40 of these is a genuine chore," that instinct is right. Keeping track of the fixed block, generating one sticker at a time, resizing, handling transparency — the fun of crafting a good prompt and the patience it takes to finish all 40 are two different things.

One photo, one conversation: describe the vibe instead

Stampo is a LINE-sticker-specific service that hands off everything covered in this article — locking the character, designing variations, matching the spec — to AI. There are just three steps.

1. Upload one photo — of yourself, family, or a pet
2. Describe the vibe you want in conversation — "soft and gentle," "bursting with energy" — no prompt syntax required
3. Check the result with a free style preview, then generate all 40 stickers plus 8 spares in one batch

Character consistency is handled by the service itself, and formatting to LINE spec — 370×320px, transparency, all of it — happens automatically. After generation, you can fine-tune phrases and expressions sticker-by-sticker in a browser-based editor, then export straight to a submission-ready ZIP. One set is $8.99, and the whole thing runs in your phone's browser.

It's a shortcut for anyone who wants to finish fast without falling down the prompt-tweaking rabbit hole. And if you'd rather build your own, you can still generate a full set as a first draft, then go back and refine the emotion map from there.

Related reading

• How to Make LINE Stickers: The Complete Guide [2026]
• 7 AI LINE Sticker Tools Compared [2026] — Bulk 40 Pack, Auto-Spec, Pricing
• Are AI LINE Stickers Banned? Rules and Disclosure Requirements [2026]