Haven't been playing at all lately, but I still keep tabs on spoilers, in case I ever come back I suppose? Anyways, Gleaming Barrier (http://mythicspoiler.com/rix/cards/gleamingbarrier.html) looks like a good addition here. We don't care if it has defender, it has the low power we want to recur it, and every time it dies, it gives us a Treasure token (which is amazing, since we can hold onto those for however long we want, AND you sacrifice the tokens, which is great for Marionette Master triggers if you wanna do the artifacts subtheme). The 4 thoughness is nice to help with the pillowfort idea anyways, and it's cheap to cast too as most walls are.

We've got another decent contender so far in this season's spoilers: Dusk Legion Zealot.(http://mythicspoiler.com/rix/cards/dusklegionzealot.html). Between the two you get your pick of mana or card draw.

This expansion is a potential treasure trove for Shirei: Pitiless Plunderer spoiled today. (http://mythicspoiler.com/rix/cards/pitilessplunderer.html).

Looks like a really fun deck! I been looking for a commander that won't go crazy on me budget wise, and this commander looks like a lot of fun!

Urborg Justice is a card that could be fantastic for Shirei, who has no issue dumping a bunch of creatures in the yard in any given turn.

Skyscanner and Desecrated Tomb look like important additions to an artifact/token theme Shirei deck. Skittering Surveyor seems handy too. If/when I come back to playing, that's definitely what this is going to turn into.

Going back to Ixalan also gives me Pitiless Plunderer (thanks shub!) Gleaming Barrier is also great mana and (non-creature) artifact token creation, Dusk Legion Zealot has great potential but it's risky if you use it too often.

I'm hoping for something good in mono-black with Undergrowth from Ravnica, but we'll wait and see.

Only thing I'm intrigued by in Ravnica is the [Burglar Rat], but I'm unsure if it want to remove any of my current discard creatures for it.

Correction. [Mausoleum Secrets] is the monoblack undergrowth card we wanted. Excellent cheap instant-speed tutor that can hit anything we need. Just 6 creatures in the graveyard (most of whom will come back at EOT) let's us tutor for 99% of our cards. Note that artifact creatures work too if you're going that route. Probably worthwhile to replace Beseech the Queen for this.

Shambling Ghast?