Thats really a very open question to answer, there are soooo many different types in many different price ranges. If its your first backquiver, you dont want to go and get the fanciest, most expensive kind you can find in case you find out you dont like 'em! You'll get lots of good advice here from fellow tradgangers on who has made them a good one.
My advice would be to buy a cheap, older one first, modify it with anything you can find like belts, cloth, whatever to try certain straps, attachments etc. Not for a finished quiver, but just to get an idea of what you want. You might like a backpack style, a single strap straight off the quiver top, one that has the strap slightly angled off the top, or possibly a three strap quiver that keeps it from flopping around and attaches to a d ring in the front. You may want a 2" wide strap while some guys like a thin 3/4 inch strap . Find out how deep you want it. Standard quivers usually come 22" deep. Thats often a lot of arrow sticking out for some guys. Do you want your fletch totally exposed or partially covered... so if you even duct tape cardboard to lengthen your old quiver it will show you what you really need. Or even cut it down if its too long.
Once you have this ugly prototype all set to your liking, you can go and either invest in a solid quality quiver by one of our leathersmiths and give them pictures and measurements, or cut the quiver apart and use it as a pattern to make your own.