Did you think that a pair of crutches could be the creative design element for shelves making? It is interesting, but it could be. First, transform the crutches to make them very strong to support the construction, and then add the shelves.
There are a lot of things could be repurposed into shelf set. For instance, an old table could be the good base for such an interesting project. The idea is really simple but too original. All you need is just to cut the table into two lengthwise. Then stack two halves one above another, so it will become your unit.