With gif images, you need to write supporting code to animate them in game. A gif doesn't animate on its own, so what you are left with is a 255 colour limitation, no semi-transparency (which is needed), and no animation.
If you add them as a texture directly (instead of just texturing somewhere for them to sit), it will be flattened when you export the model's textures, and you'll just have the first frame. Just like how when editing Cricket 07, if you import a gif, it gets turned into a bmp of the first frame.
And if you are having to write code, you may as well use something more advanced than a gif. If you don't want hundreds of files with frames of animation, implementing ANG (Animated PNG essentially) would be just as easy as implementing GIF. Might make the game more difficult to edit, as not many programs can deal with ANG images, but saves making up a proprietary container for all of them (by including them in the one file, they can be saved as the difference between the previous frame, saving space on the disc compared with the complete image for each frame).
For me, the best implementations would be to make it a flat crowd (a snapshot of the 3d crowd), that animates in 3d when you actually are close enough to see detail. You don't need slight bobbing up and down animation while you are bowling, but if you cut to a shot of the crowd, you can render that nicely (in times when you aren't focused on making things as smooth as possible).
The crowd isn't dancing all the time and can be distracting if it is.