This is a bit of a stretch, but if you have matlab, you could use a matlab script node. They have a very large standard image processing library. But you might as well use Matlab for the project. Similarly, you could also use c code nodes, or compiled dlls, but this is overkill for labview. You'd probably do better developing natively in something else, rather than writing dlls for labview.
As for LV practice, I hate to rain on your parade, but do you know how many man-hours go into a toolkit for Labview (or for any programming language, for that matter)? I assure you that you will spend more time repeating other's work than doing your own. Remember, your time is money, too. Assuming you are an engineer, two weeks of your time is definitely more costly than a license. If you're a grad student, I can sympathize (I wear both hats), and I've heard the "make it work" message.
so much for "how to paint a house without a paintbrush"...
- Jon