In order to improve the performance of our Marketplace, we've worked out some recommended sizes for icons & screenshots. This was necessary because the marketplace homepage contained 16MB of assets on an uncached request.
Short summary of the recommended sizes:
- 400x400px in PNG format
- First screenshot should have the size of 600x405px
- All other shouldn't be wider than 1200px
More information about screenshot content guidelines, instructions on how to take a screenshot, and tools to optimize the file size can be found on the corresponding documentation page.
As a side note, we are already under 5MB on an uncached request! ð