Fredrick is near Morgan's ship, actually, and Gaz can have him come out and notice any time.
I always imagined Jagill as a battle worn Hork-Bajir that's big and buff even by Hork-Bajir standards. He has a big scar on his chest, and a few more here and there. If you draw him, a battle stance would be cool.
As for Claxter, he's around Ax's age. I haven't thought up any particular features for him. Just your average young Andalite. Maybe give him a bit of a nervous look.