Hi Leonor,
The max dimension size is 600 x 600. I noticed that your last layout was 512 x 512, so if you upload the same size you should be okay.
There is also a limit to the size of the file. It needs to be less than 180kb. Your princess layout was only 65kb, so that would be fine, too. Whatever you did with your princess layout, do to this new layout, too.
