If you mean by "bob" your own driver, then click on your icon in GT-Life. From there you can select your racing gear and take a picture. (You can choose 1 from 9 different pictures.) Once you selected a picture, it will be automatically your in-game avatar.
(please correct me if i'm wrong with anything. Thanks)
Refer to above post for your own character. For your b-spec drivers, just go into a replay of one of their races and take some pics. Works best if they're driving a go-kart.
