A costume is an alternate sprite sheet for one of the characters already in the game. Designing a new costume requires an image editor and nothing more
Go ahead and pick your favorite costume from the Community series. Then take a look at the Costume TODO Spreadsheet. Some popular costumes have been completed, but many remain half-finished. Sign up for one and get going.
First, you'll need to get the base sprite sheet for your character. Choose your character from the following list.
Next, open your sheet in an image editor and start designing. Please make sure to keep the dimensions of the sheet and the placement of the sprites EXACTLY the same. This means individual sprites MUST fit into a 48 x 48 pixel square. Doing so allows you to easily test the sprites in-game and makes it more likely your costume will make it into the released game.
If you have any questions about the character's sprite sheets, please see the Character Creation Guide.
The Hawkthorne Costume Tester allow you to preview your costume without having to run it in the game. Once your sure it looks good, then you can submit it to the subreddit.
You can submit your costume by posting a costume-tester link on /r/hawkthorne or opening a pull request on this repository.
Here is a one of the many costumes we have in-game. Say hello to Evil Abed. The artist stayed within the 48x48 boundary, and added creative pieces such as the goatee and cigarette that made it more like the character. Make your costumes unique! Changing the color of a shirt isn't enough.