I'm going to second elpablo's suggestion that you narrow the color spectrum for your deck. For whatever reason, the M14 slivers might as well be from a Naya shard than something five color. Without all stars like Sliver Queen, Sliver Legion, and Sliver Overlord, there really aren't reasons to slide in those extra two colors.
This is a ROUGH build I've pieced together that would focus on all post-rotation viable sliver pieces (and lord knows what Theros will give us in these colors).
Creatures
3 Elvish Mystic
4 Manaweft Sliver
4 Predatory Sliver
3 Sentinel Sliver
3 Blur Sliver
4 Bonescythe Sliver
2 Battle Sliver
Instants and Sorceries
3 Hive Stirrings
2 Mizzium Mortars
2 Shock
2 Celestial Flare
Planeswalkers
3 Domri Rade
Artifacts
2 Door of Destinies
Enchantments
1 Collective Blessing
1 Primeval Bounty
Land
4 Forest
2 Mountain
3 Plains
4 Sacred Foundry
4 Stomping Ground
4 Temple Garden
Now I'm not saying this is an optimal build by any stretch of the imagination, but you'll note that it has some added diversity to help out your plan. I think it's an easy mistake to make to simply slide in all slivers and nothing else, but you will encounter creatures or other things that you simply have no answer for in your current setup.
Lands aside, here are some thoughts on the archetype:
1) You're still sitting on a pretty creature heavy deck here with 23 creatures, 20 of them being slivers. The Elvish Mystics are really just meant to offer another mana accelerator and they could easily be replaced with some lands or other spells/slivers.
2) Realistically, you are going to run into threats on their side of the board that you will have to answer. Whether it be Olivia Voldaren, a planeswalker, or something else, if you go the 100% slivers route, you have no means to deal with their board threats. Simply put, I could see Angel of Serenity, Kalonian Hydra, or even Archangel of Thune single-handedly taking you down. The addition of some point removal is critical. In this build I've proposed you have a variety of options ranging from Shock for disruption, Celestial Flare for larger threats or hexproof creatures, and Mizzium Mortars for larger threats. Keep in mind these are by no means the only options available... the sky is the limit, but you NEED at least some versatility.
3) Personally, I'm not a believer in the slivers that cost more than four or five mana. Giving them all trample might be nice and all, but you could be doing more for seven mana than just playing Groundshaker Sliver (if you're needing trample that much, Skarrg Guildmage is out there... and there are other options). Further, Megantic Sliver works wonders in limited, but in a constructed environment, it will get wiped out more often than it will do any good. Rather, what I suggest are a few six drops that are in your colors that will have a bit more effect. Collective Blessing is the exact same thing as Megantic Sliver, but it's an enchantment, making it harder to deal with. Further, Primeval Bounty creates a card advantage engine that the opponent likely won't be able to overcome... it will turn that t7 Manaweft Sliver into a larger threat with an added 3/3 beast token, late land drops become life gain, and your removal will serve to further pump your slivers. I just see this as the sort of answer to drawn out games much like Assemble the Legion has been in some upper tiered decks. Again, just my two cents lobbying for a card... take it or leave it. But the key here is to be making some more headway when you're spending 5-6 mana rather than just dropping a sliver who will get blasted immediately.
4) I really do think Domri Rade really works in any sliver deck... he creates added card draws and offers spot removal. What's not to love here?
5) Door of Destinies... tribal deck and you're not running at least 1-2 of these?
Anyway, I'll leave it up to you to decide what to take or leave from this proposed build, but the key things to think about when running with slivers is to reduce your colors to improve consistency, add some non-sliver cards to increase your versatility and flexability to deal with other threats, and rethink the top of your curve.
Best luck with it!