There are a lot of issues involved in setting up an online clothing store. You should look at :
- A business plan for starting including your budget for hiring a good web developer to develop your new website
- Strategies for creating awareness of your new site (SEO, SEM) on the internet.
- Inventories management to avoid stock piles up in your store room.
There are more issues but you will learn along with running the online store.
Cindy from http://www.curvysea.com
You can order t-shirts online and just upload the picture that you want printed on the t-shirt while checkout out. I went with a company that I really enjoyed working with at the source below. Check them out, they have cheap prices on custom t's.