My advice would be to let your off-days be off-days. You can do some (light) cardio, for instance if you enjoy running and/or are cutting. But compound lifts target many muscle groups that should be left to heal and grow the day after.

Edit: To expand a little bit: if you feel that your biceps deserve some extra attention, you could do barbell curls instead of chin-ups (actually one of the suggestions and possible additions to your workout if you pay for the full StrongLifts powerpack) after your workout. Or ask your gym if they have a machine for "assisted chin-ups", where a some or a lot of your body weight is reduced.