Because of the high cost of most of your big creatures try adding in Elvish Piper and Quick Silver Amulet, also an Emrakul or two. Because its Bant colors also possibly try adding Noble Heirarch for mana.
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Replace paradise for gemstone mine so it stays longer, instead of elven cache use recollect because its a green mana cheaper. Charm, powersink and three wishes sideboard and put in demonic, infernal, and mystic tutors to help draw out combo. And try to make room for a second recollect/ cache just in case you don't draw into another prosperity after the 1st go. Just my own preferences I use in my version. Otherwise great build of a classic deck, nice addition with force of wills.
If you're going to run cowardice add jolting merfolk. It's ability combined with cowardice means you can get rid of 3 opposing cards and then bounce merfolk to reuse.
With this much control/ output destinies takes up too much mana to care about in my opinion. Maybe get rid of lanterns and side spotlight for some dissipates?
maybe try oath of druids?
@Benny_boy: While 5 colored slivers are fun there is just not enough space nor consistency to warrant adding the blue or black slivers in standard, in other formats these would rock. I chose to go Naya colors with my sliver deck because of the ability to add some element of field control. Here is my build. http://www.mtgvault.com/serriz/decks/naya-sliver/
Make bant slivers with splash red, turn 1: virulent, 2: mana sliver and virulent, 3: shroud and flying sliver and maybe another cheap sliver, 4: swing and win, using splash red for haste sliver/ burn for opposing flyers.