Heh, don't sugar coat it jg
I would agree with it all, and if I may, add my own suggestions.
Is there really a market for this sort of thing? Oh wait.. I've just read the site a bit more. The first impression I get is that your site only sells posters of dogs, so I was confused that you had mice and cats in the pictures at the top. Perhaps your homepage should be more generic - "Animal posters" for example.
Also, I'd recommend shoving your most popular poster right in the face of anyone who drops by. It should be the first thing they see, along with the text "Have this on your wall" or "Buy this poster now" or something similar, demanding action from the user.
Lastly, jazz up the colour scheme a bit. Dull grey is not exciting. Neither is maroon. Perhaps try orange, bright green, bright blue, yellow, purple etc.