My favorite saying that has always helped me is KISS which stands for "Keep It Simple, Stupid!", and it works. Instead of trying to show your blistering chops, go with something simple as, more often than not, that'll sound a heck of lot better. It is, after all, a band, not a solo project; you have to work together and listen to each other.
A nice improvisation device I like to use when trading fours is imitating lines which the instrument before me has played. Also, I agree with the various previous suggestions of repetition as well, as that gives your solo structure, and something the listener can relate to.
Anyway, that's my take on that, hope that helps, mate.