Well.....I took a looksie and it looks super sharp. I think you've done a Great JOB!!! Now - remember I'm Queen Numpty, so all that I offer is with no experience

!!!
Is it possible and logical to perhaps add another page/area to your site that explains what zencart is and how to best use it? When I write anything, I always assume my reader(s) are k-garden level or lower - thus try to explain

(using tons of key words) exactly what, why, when, who, etc.
For your site, you can (if desired, and if logical) detail out ----
- Zen Cart
- Template
- Banners
- Logos
- Customization and how it works and why
- ETC.
I see to the right, you have links that discuss your items, zen-cart hosting, etc. - perhaps there. If you don't think these things need to be on your site, all great topics for a blog or a squidoo lens - that link backs to your site.
Does this make sense? One thing I've picked up on is that search engines do like great content. One way to embrace key-word rich content is to define and suggest.
I do love the colors - close enuf to blue with navy ---- super cool!!!
