Great, thanks for these comments. I was cobbling it together this morning (total development time so far has only been a couple of hours) so I have some unnecessary stuff in there for sure. I will simplify. I'll also think about including multiple images per project if possible. Still not sure about the whitespace being an issue, but I did just throw some mediaqueries in there to help with the header on smaller resolution devices...
edit: I just stripped out a bunch of the extra stuff and everything seems to be working and it all validates. Also, slimmed down the space between screenshots on smaller resolutions, tweaked the color to the arrows, did some other stuff. Man, I forget how much I love playing with code...