Mash the avocados together in a bowl with the garlic and lime juice until your desired consistency is reached. Stir in the onion, salsa, and cilantro, then season to taste with salt. Set the guacamole aside.
Stir 1/2 cup of the sour cream together with the mayonnaise and 2 teaspoons of the taco seasoning in a small bowl until thoroughly mixed. Set aside.
Spread the beans evenly into the bottom of a 9x13-inch baking dish. Spread the seasoned sour cream mixture evenly over the beans, then spread the guacamole over the sour cream mixture, being careful to not mix the two.
"Draw" your football field lines on to the guacamole using a knife tip or a toothpick - you will use this etching as your guide when drawing the lines on with the sour cream. Place the left-over sour cream into a small plastic sandwich bag and snip one corner of the bag. Push the sour cream through this small hole to draw the football field lines.
Place 10 tomato halves (5 of each color) on the field into "playing positions" Dice the rest of your tomatoes and add them as "filler" to the end zone areas (you may have some tomatoes left over).