Love to see this, never heard of the engine before so IDK what your limitations are - even with the down scaling of the sprite its a pretty neat looking character, maybe just because its not another peasant / noble / space marine (not that I judge peasant protagonists, its popular for a reason, but standing out has some value as well I think)
Did some research, have you tried the "Better image uploads" addon?
Again, I've never heard of this engine, I just searched their github and this was an issue about images over 260x480 2 years ago. Here's where I found the information:
https://github.com/ScratchAddons/ScratchAddons/pull/2525
This comment section is getting pretty crowded, I opened a KoFi page yesterday - that's a better place for suggestions and discussion: