Place triangles together on 12x10-inch piece of plastic wrap to resemble a tree. Cover with second 12x10-inch piece of plastic wrap. Press to flatten cream cheese tree into 7-inch-tall tree with 6-inch-wide base. Peel off top sheet of plastic wrap. Invert cream cheese tree onto serving plate; remove remaining plastic wrap.
Mash avocado in medium bowl.
Add mayo and lime juice; mix well.
Spread over cream cheese.
Cut 3 thin slices from pepper; place on top of tree. Seed and chop remaining pepper. Decorate tree with peppers, tomatoes and onions.
Place 8 crackers, in 2 stacks of 4 each, at base of tree for the trunk.