What kind of nut/seed snack foods don't aggravate diverticulitis?

High fiber! The idea that folks with diverticular disease should avoid seeds, nuts, corn, popcorn has never had any data to support it, so unless a particular food item causes discomfort, i don't advise its avoidance. That said, those with diverticular disease should be on a high fiber diet with plenty of fluid- this has been shown to decrease episodes of pain.
Careful. If you really mean diverticulitis, stay away from any fiber until the diverticulitis has completely reolved, about 4-6 weeks. If you mean diverticulosis, then a good high fiber diet and plenty of fluids in excess of 80 ounces per day not counting caffeine or alcohol is the appropriate regimen to reduce incidence of diverticulitis.