I don't like that street creator trophy pieces are trade-able and buy-able. You should have to earn your pieces! (I have traded and bought and sold and given away, but I do not like that this is the system.)
To make this not insanely frustrating:
a) Stop giving so many duplicate pieces. Keep track of which pieces a player has already earned, and only give new ones.
b) Associate different phase types to each trophy. Say, maybe to get earth pieces, you'd have to work on the phases that are block/peat/earth/loam heavy. Or Phase 1 always earth, Phase 2 always wood, etc. Or it could be random-ish, but the project description could say "The top five will get a rock trophy piece." Most importantly, make this fairly transparent, so people can tell what is going on.
c) Give the trophy pieces to the top 5 who have not already completed the associated trophy, but keep the xp/energy/mood boosts tied to percentage donation. Give a diamond or something to people who would have gotten a piece, but already have the trophy. (So if #1 and #4 already have the trophy, they would get diamonds, and #2,3,5,6,7 would get trophy pieces.)
Also, at the moment, the names that go on the street seem to be connected to what happens in Phase 4 only. Please make this instead a function of overall contribution throughout the 4 phases.