The only question I can answer is that I can't provide a high res version of the PGC logo.
As far as how long you have to wait after winning one contest, I have absolutely no idea. If there's a rule about that, I don't know it. I'm judging this based on the quality of the pictures sent in, so unless Jonny expressly says, "Hey, no letting people who won within the last X number of contests win," it's not going to be a factor in my decision making.
EDIT: Monitor photos are okay. Also, I'm going to clarify the Photoshopping issue: Adding text is fine. Altering the images in a photo is not fine. If there is text on something you took a picture of, (i.e. a shirt, book, etc.) and that text is altered, that is considered altering the image. However if you take a picture of yourself with a Burger King crown and added Purple text saying, "King of PGC!" that would be acceptable, albeit lame (no one has done that, I just came up with that idea--which is probably why it's lame.)