Some sites, e-quilter, fabric.com and others I can't think of right now allow you to add fabrics of your choice to a design wall. Then, you can see how they look together. I have ordered fabric on-line for several years now and only once or twice have I been disappointed. I believe that if you are ordering from someone like Keepsake Quilting you would have success talking to someone on their phone lines. I've never tried, but they are very consumer oriented.
If you see a fabric you like in a magazine, you can go to quiltshops.com and do a search for that collection. That can often help if you know one fabric but perhaps can't find other pieces of the collection.
Have fun shopping in your pj's.