Redesign/improve BigCommerce,Advice on Ecommerce/SEO

I am a online computer reseller that use bigcommerce. I used standard template thus its pretty plain, it needs a lot of graphics to create more atmosphere for customer to buy. I want my web site to look young, refreshing, solid, reliable, informative, simple to use, so you need to have extremly good understainding of online customer behavior. e.g how to make website viewable, flow of website, check whether there is a problem, why customer not attracted to buy. Also need to redesign the logo, and business card... etc Ebay template to match the web store. Most importantly is the graphics on my web site. So need someone who is extremly good at CSS, illustrator, photoshop, web site deisgn..etc I need professional artist. I dont like graphics look unprofessional on my web site. Please do not apply if you are only an ametuer design artist or semi-professional. I want real professional!! I need the website to look GOOD, (yes very important) so to create the hype for people to buy. Please send me some of artwork / sample of site you done. Also important is, I need a capable, flexible, transparent, reliable, honest, ethical freelancer /company.. pls inform me your code of work . If youre a company with registered business in local countries, it will be even better. Pls show me your certification. Also you need to create the template in photoshop for me so I can update the product as I expect to update my website weekly. Also this is is not a once off job, its long term relationship, as my site constantly need update for special occasions e.g Easter, Xmas..etc. But I have to see how you go first... Also, please advice ecommerce plateform which is suitable to my situation, should I continue to use bigcommerce or use something else. I need to have a site that is link to my supplier for stock level. Also need advise on SEO. So its better if you know all of above.