Thank you for your question.
I use a photo album to do the same thing that you want. I use Gallery
for this, as do many people. For an album to display photos to your
potential customers, Gallery is a professional-looking, simple and
reliable interface and program that should work perfectly for you.
However, Gallery only works if you already have a website up and
running. If you do not, you will want to use a web-based solution.
Here are a few different ideas for that.
Many people use Flickr, and if you already have a Yahoo ID, it
coordinates well with Yahoo because it's owned by Yahoo. It is
professional-looking and a reliable site that would well for
Yahoo Photos doesn't look as well-done or professional as Flickr, but
it would work for the same purpose. It also has unlimited storage.
For pictures on Ebay, you will need a hosting service with good
bandwidth. For this, I recommend Photobucket. They have pretty high
bandwidth for their free account and I have used it for image hosting
with great success. I hate the name, but I like the site.
You could also make your photo album on Photobucket public for
everyone to see, but you might not want the name to appear on your
professional business cards (or maybe you do, I don't know!) Either
way, Flickr or Yahoo Photos should work well.
If you need any additional clarification, let me know and I'll be glad
to assist you.