First of all, register here: https://creator.line.me/en/
Read the guidelines before starting:
You are going to need to make a total of 42 images. 40 will be stickers, 1 will be the small button for the stickers (chat room tab image), and the other image is preview image for the sticker store (main image).
|Main Image||Sticker Images||Chat Room Tab Image|
Size: W 240×H 240
Size: Max W 370×H 320
Size: W 96×H 74
Making the stickers.
I recommend using Inkscape - please remember that although these might be the suggested size requirements now, someday you may want to use a larger size for a different messenger or for some other project. The great thing about Inkscape is that you can make the pictures as big or as small as you want and it will still look great.
Some things to note, Line can be very picky. You might have to change your pictures several times before they are accepted. It may be a long process and you may have to wait a considerable amount of time, but it will help you learn about the process of creating a professional piece of art.
40 images may seem like a lot to make, but don't get lazy! Line will not accept your images if they are too similar. Make sure that each image is as unique as possible without having any of the stickers seem out of place.