Dear Dude. I've looked at your website. First of all you need to still concentrate on the layout of your website. Then sign up for google webmaster tools, create sitemap, and update your website atleast 3 days once. Get different backlinks from different IP's. Share with twitter, facebook, linkedIn, Digg, etc.. Buy reviews from bloggers. Also sign up for google adwords. Do it regularly and im sure that you will get more traffic for your website. But the only thing in SEO is we should be patience and wait for the results. Thats important. All the best..
working on the layout and making it "trust-worthy" will encourage visitors to stay and keep browsing.
You need to do seo and get your website out there, You just need to know what you are doing and I'm sure you will do a good job, Try using Yahoo Answers, maybe even do some Social bookmarking
What I do for my shop site is bookmark its urls as and when I publish pages, write articles and product reviews with links to the site. I make more from the adsense on the sites and articles than I do in affiliate sales.
SEO is important. Make sure you give each product a good keyword that isn't competitive. You'll have hundreds of people rolling in within a few weeks if you do your keyword research correctly.
I think before thinking about all the SEO effort, just like many people say, first concentrating on working out a better layout first. A better layout means a better browsing experience for the visitors. Based on your website, at least you need to make the menu bar more obvious, for example using dark text on a plain background. Also if your main focus is selling posters, then try to allocate more space in the page for that. As I look at your site, the banners simply take too much space. I believe all these little things add up to better credibility and usability of your site. Hope this help!