I'd recommend oyster mushrooms, which is what I thought ecovative used initially. It's an extremely aggressive grower and will out-compete most everything else. Steam sterilization with an autoclave or large pressure cooker works great for spawn bags, but if you want to do really large scale stuff, I'd recommend straw pasteurization with a 50 gallon drum. Oysters are also great because they aren't picky when it comes to substrate usually, they'll grow on wet cardboard, newspaper, coffee grounds...you'd have a tough time getting a shitake to spawn on that.
I've been reading up on straw pasteurization with hydrated lime but have yet to find the low magnesium kind which many people swear is important. Iv'e tried wood ash (sort of half-assed) with poor results. Trichoderma or whatever else was on the straw took over every single bag, except the bags with oyster mushroom spawn in them. The oyster spawn crushed them.
If you want to be able to sculpt things, I'd think about a mixture of media, with straw, paper, sawdust, etc that you can form into bricks or shapes that will hold once it's colonized.
As for a brick once it's colonized, I know people that use a 0.1 % hydrogen peroxide solution in water for misting. The thought is, it'll kill any bacteria or young fungal cultures on the outside of the spawn brick, but won't do enough damage to the mycelia that's already taken it over.
Timing is important if you want to keep it going, because once a fully colonized brick is exposed to oxygen and moisture it will probably pin and grow mushrooms, which I suppose could give the sculpture a really cool look as different pieces are pinning at different times.
You can control the pinning with CO2, moisture, light, and temperature. I would completely forget about using boatloads of antibiotics or some transgenic mycelia, nature has already given most fungi pretty good defense mechanisms against bacteria.
shroomery.org is THE go to place for all things fungi. There are plenty of great threads there on edible mushrooms, not just the psilocibes.
I have cultures of white oyster, elm oyster, pink oyster, golden oyster, blue oyster, and king oyster you're welcome to a petri dish of