I do not buy veggies in cans, so our choices are frozen or fresh. I try to keep our basics on hand in the freezer: green peas, green/snap beans, corn, and broccoli. I rarely buy mixed veggies -- mostly peas and carrots. And, if I have a recipe that calls for a given veggie mix (California mix, for example), then I'll buy that. We're pretty boring when it comes to the veggies we cook & eat. Squashes are cooked from fresh. I rarely cook cauliflower or asparagus. And, of course, I keep fresh onions, green peppers, celery, and garlic on hand. We do eat a fair amount of raw veggies -- particularly in salads -- so that adds a lot more variety.
I really like to take advantage of the bulk frozen veggies at Costco. I'll buy one of their 5 pound or 10 pound bags (I forget what size they are) and then break it down when I get home. I put 1c of corn/beans/peas or 2c of broccoli in a sandwich baggie and then put all the sandwich baggies into a gallon or 2 gallon freezer bag. I can then take out pre-measured portions to cook for a meal/recipe.