I was was having trouble recently trying to upload a photo into Projects, and after trying all the suggestions from other Cuties, I finally found that it had nothing to do with the size of my file, but was a feature of the security program my son installed for me. I had to give permission for the upload to occur. Do you have NoScripts or a spam filter that could be causing your problem too? Bev.
Another thing that happens is they take a while to show up. You might submit a post but all you see is a box for a couple of minutes.
The fact that you downloaded 5 pictures at the same time has nothing to do with it. I make them as small as 100 to 500 KB and they have to be in a JPEG format. You could re size with most Photo programs or Paint which is in the accessory folder of most PC's. Hope this helps.