Crappie love live bait. They are not a scavenger fish like catfish or some other types of scum suckers. Live food generally means more protein and more energy and with crappie if it they can fit it in their mouth they will generally eat it. When it comes to live baits there lots of types like insects and their larvae, reptiles, invertebrates, amphibians and of course the obvious one: other fish.
Of course I am one of those guys that if I can get it on a hook I'll give it a shot, just think about how it might look in the water. Not that I'm suggesting anything but even the cotton from a cigarette butt works from time to time. Also I'm not a biologist so I will group some types of live bait into a category that I think work but not necessarily a category they belong in.
Insects are those creepy crawly bugs that are big enough that you wander if you step on it, it might push back, this includes spiders although they don't like to go onto a hook and don't always work out so well. If you choose a spider pick one that doesn't bite.
For the most part I use large winged insects on small hooks. This can be tricky as well because most of these insects have a couple of problems. First you got to catch them, get them on the hook and lastly they come off the hook easy so be ready. Mealworms and maggots work great to tip a jig with or ice fishing.
Small lizards and snakes are not common in many bait stores but can work magic in the right location. These squirmy creatures can provide lots of action and when hooked properly seem to live a long time, not to be super cruel but these guys do need air from time to time.
Invertebrates like worms and leeches work really well in dark to clear waters but beware leeches are not allowed in many bodies of water. This is for good reason. If the waters to not already have a balanced system that can support leeches introducing them can decimate the entire eco system.
This goes for all live baits be sure and check that you can use them where you are fishing or the next thing you know you will be fishing for goldfish instead of crappie. Worms provide lots of protein for fish and will act lively for long periods. Hook a leech through the mouth but hook a worm in a way it won't get stolen without a bite on the hook.
Frogs and toads also work really well because they are often a source of food for crappie already. Tadpoles as well as young critters work well. I find that once they are bigger than a quarter or a 50 cent piece they start to attract other fish.