I took a look at OS Commerce
– a brief look. It appears that this package does a lot of the “business” including an interface with payment services like Paypal. It may be everything you need to establish a web-based business.
OS Commerce may also provide a template for your web pages. For instance, they have a catalog page in their demonstration area. By replacing their images, information and links with your merchandise, you can then publish your catalog to the web. If that layout doesn’t suit you it could be modified.
The way I “looked” at the page was to copy the page source code into KompoZer
, a free WYSIWYG editor. That clearly showed the tables used to format the page. Each merchandise item has its own cell in the table so adding or replacing content would be easy – once the page was set up.
Part of your question was on content, logos and all the other stuff that makes a web site interesting. Your suppliers should be able to provide images for your catalog. If you are making your own product then get a good, digital, probably SLR, camera. Someone could do your logo in PhotoShop, Gimp or similar package. Because I like to do things on the cheap (or free) I use PowerPoint to create and FastStone Capture to crop, size and save the image.
At first glance OS Commerce seems to be a heavy-duty package. You may want to ask their support community for advice. My thought is if your business requires all that OS Commerce offers then you may need to focus on the business and pay someone to set up your web site.