Board Thread:Questions and Answers/@comment-29058994-20160716164928/@comment-6697950-20170616181156

I don't know about any maximum dimensions. The only limit I know of is the 10 MB limit for any file. Though .png format files tend to be crash-happy when they're over 5 MBs.

And yes, downsizing files is permitted. We've been doing it for exceedingly large files for a long time now.