If you're uploading as an attachment the size and dimensions are restricted to
png 19.5 KB 620 x 280
Relatively small. I would find an image upload site that allows hotlinking to forums like this. If you wait a while someone will probably be able to give you a name of a good one and then you won't have to upload and just use the insert image option where there is no restrictions to very small image sizes.
Try to upload this screenshot I've uploaded from Googlesites.
I have no idea about the filesize but I hope it's not that large. Oh, well. I can always show screenshots while I make a new hack release but posting screenshots while I submit would be better so people can look at it and see if people can download the hack from Zophars (after approval).
I already have a direct download file in my own site but I need to back it up just in case something bad happens to my site.