Hey @EA_Kent thanks for the reply!
I've tested this on multiple browsers (specifically Microsoft Edge, Google Chrome and Opera GX) and directly from my desktop computer (I also tried my laptop). My computer is Windows (desktop is Windows 10; my laptop is Windows 11).
I even tried to create a new EA account (on a separate e-mail I have) to see if it was account related, it doesn't seem to be since the account change didn't fix any issues. I also tried to rename the photos/logos I was uploading to see if somehow the file name was causing an issue or something. Even went as far as resizing the images/logos even smaller thinking that maybe the sizing bugged out and was causing an issue. Heck, I went to the extent of creating a "logo" myself (simply just took the letter "W" and created an .png image file of it for uploading) and that also got flagged with the "failed validation" message. And for what it's worth, the EA logos themselves (the ones that are generically applied to new teams) ALSO got flagged.
I hope I was able to at least give you enough information to help fix this. This is incredibly frustrating for us gamers and I imagine it's just as frustrating for y'all.