How to properly export collection assets
Our tool works by stacking traits from various layers and composing them together in the order that you specify to form a unique (and probably awesome-looking) token. In order for this concept to work, you'll need to bring your own assets (BYOA), and they need to be formatted properly.
There are a plethora of tools you can use to compose your trait assets: Figma, Adobe Illustrator, Adobe Photoshop, Procreate, and even Inkscape! The tool you use doesn't matter as long as the traits are exported properly. Each file will need to have the same dimensions and exported in either JPG, PNG or SVG format.
From your illustration tool, you might find it easiest to pick dimensions for the whole canvas, then compose a token to use as a starting point. Ensuring layer traits stay consistent will likely be crucial to ensuring a consistent token throughout the collection. For example, if you plan to add a "shirt" layer, you might want to keep each shirt in the same position of the canvas for each shirt trait, then only alter the color or style of the shirt as needed.
However, we really don't care about your methodology of trait creation as long as the assets are the same size! We don't have any file size constraints...yet (don't make us add them!). Lasagna can handle some pretty massive files, but keep in mind it will likely take us longer when it comes time to composing and "printing" your tokens if you are using larger assets. We find that 1024 x 1024 pixels is a pretty excellent canvas size, but we'll leave it up to you.
However you decide to make your artwork, make sure you have fun with it.