The following considerations are important if you are thinking about a vegan diet (anyone please feel free to add to this list if I forgot something):
- protein (include sufficient amino acid diversification and sufficient quantity for your goals)
- calories
- B12, Iron, Zinc, Calcium
- Omega 3 fatty acids
A multivitamin can get you B12, Iron, Zinc, and Calcium. With regard to Omega 3 fatty acids, you can take algae Omega 3 supplements (this is actually why fish oil is a good supplement for getting Omega 3s; fish feed their fat little fish faces on algae).
With regard to protein, if you are strength training, it will be helpful to drink a protein supplement unless you want to be eating tofu and seitan all day. A good one is Vegan Protein Optimizer by True Nutrition. It actually has iron in it, so since some multivitamins don’t have much or any iron, you can get your iron there.
Also, many plant proteins are not absorbed as efficiently as animal proteins, and they are lower in certain amino acids than animal proteins. Thus, a vegan strength trainee will have to eat a bit more protein than the equivalent omnivore to get comparable benefits.
Vegetables and fruits are pretty awesome for keeping the pipes flowing, but most are not calorically dense. Natural peanut butter, nuts, rice, noodles, oils, starchy veggies, oats & almond / cashew milk, candy (if you have a hard time gaining weight), dark chocolate (many dark chocolates are actually vegan), etc., are good for gaining weight.
My current, cheap, college student, impatient bastard vegan diet is as follows:
Breakfast
Protein powder 1 scoop
Some breakfast thing; perhaps involving peanut butter, fruit, etc.; maybe protein bar
Snack
Protein powder 1 scoop
Black beans
Big salad with lemon oil and raspberry vinegar
Lunch
Protein powder 1 scoop
Big-ass natural peanut butter banana sandwich on wheat bread
Big salad with lemon oil and raspberry vinegar
Dinner
Protein powder 1 scoop
Lentils / rice / tofu chili / vegetable soup / going out to eat with friends
Sometimes sweet potatoes / squash & okra
Throw some nuts & candy & various other items in there (as well as the vitamins I take), and that’s pretty much it. Cheap, quick, and easy.
With regard to a food pyramid, I think you would obviously include fruits and vegetables. Everyone should have those in their diet regardless of whether they are omnivorous, vegetarian, or vegan. You would want to include some fats as well. Peanut butter, oils, flaxseed, pumpkin seed, nuts, etc. Not sure what else. Perhaps whole grains and such. Really, I think as long as you follow some of the principles I talked about above, you will be fine.