Request documentation on recommended image size/types

While it looks like it is PNG format for the time being, what are the best recommended image sizes to use per platform? And am I able to provide my own images resampled for various sizes or redrawn to represent the appropriate size? Scaling a large image down isn't always the best approach.

No file or test is identified in the issue. Research the recommended launcher image sizes and types for each supported platform, and clarify whether users may provide separately resampled or redrawn images. Done means the project documentation answers these questions with platform-specific guidance.

Written by the indexing model from the issue text.