There are some varieties that don't include the corn, so if you want corn, you can simply add a bag of frozen corn, or a can of corn.
Also, super common is a mix of just peas and carrots. We love using peas and carrots in soups, stews, pot pies, and fried rice dishes.
Some prepackaged mixed vegetables also include cauliflower. More recently I've seen a mix of broccoli, cauliflower and carrots.
While prepackaged vegetable mixes have been sold for years, the most common mix I see is a mix of green beans, peas, carrots, corn, and French or lima beans.
Mixed vegetables, whether its frozen mixed vegetables or canned mixed vegetables, tend to be relatively inexpensive and easy to find. I've seen both at dollar stores and most grocery stores.
Both canned mixed vegetables and frozen mixed vegetables have a fairly long shelf life. While the frozen variety should be eaten quicker, especially if they are susceptible to freezer burn, the canned mixed vegetables will stay good for years.
