My favorite thing to improve table image is to bet draws early. Play more suited holes...74 69 etc...on or around BB. Then if you hit the straight just play it like you hit your trips. If 4 to str8 play like a small pair and try to catch, drop it to aggression and bet small when you can without getting raised (OutSideStr8s only). No one will notice the change in the aggression later in the hand when you pour on the steam and even if they do they will be totally confused and probably call you anyway. Also, sets up great bluff opps later if you show it down and win.