You mention CrazyTalk so I'm assuming you mean CrazyTalk 8 rather than Crazytalk Animator 3.
For 2D projects in CrazyTalk 8 using your own drawings, you can use source images up to 2000 x 2000. Anything larger will be resized. I would recommend using a format like PNG or BMP rather than JPG.
With a good quality high-resolution source image you should get excellent results in CrazyTalk 8.