Old x-ray films work well as splint pattern material, for those patterns you use over and over again! The x-ray films are thin and strong, so will last much better than paper patterns.
This happens to be my old shoulder x-ray but you can ask any x-ray department and they might have some reject ones you can have, as long as there are no patient details on them.
Just draw the pattern you want onto the film and cut it out!
There are many options to store patterns and I guess it all depends on your working environment. You may have a drawer for all your patterns where they are randomly chucked in, or they may be neatly stored in a folder. Or, if you use a particular pattern on a very frequent basis, you may even want to consider hanging them on the wall by your work bench. Just attach a small velcro dot at the back and have the opposite velcro on the wall.
Room for more patterns!