Please bear with me as for that I am still "green" on playing Heroclix.

Question: Is it legal to have 3-D objects that are the same? At the tournament, the opponent chose three dumpsters, all of them are heavy objects...while I got two heavy objects (not 3-D objects - I used the buttons - hot dog stand, dumpster, and gum machine)...we put on the map, I was quite intimidated by that guy because of those heavy 3-D objects, all of them dumpsters...made me wonder if it is legal or not. Any feedback or suggestion that I will need to improve in the future?

They are only usable if all players in the game agree. It's in the FAQs. They should still pick the buttons and then replace the buttons with a 3-d object of his choice.