Well, you've got a lot of MXR and some EHX on the board. A lonely Boss tuner.
So you should get a Boss chorus pedal of some kind, to balance out the branding on the board. Based on what you've got I'll make some assumptions about what's available to you locally and what you're willing to spend – no boot-eeky suggestions.
If you want a subtle chorus, the Boss CE-2B. Even subtler, but sounds great Boss Dimension C. Either option you'll have to hunt used though.
Boss LS-2 line selector will add further brand parity to your board. The new Boss FV50 mini volume pedals look great! If you prefer, the regular-sized Boss FV500 volume pedal. The volume pedals come in either High or Low impedance.
I'd be happy to have any of this on my board, and I do have the CE-2B.
Get the aforementioned Boss selection and the board tally would be
Brand :: # units
MXR :: 4
EHX :: 2
Boss :: 4
So clearly you'll need two more EHX pedals. The new micro-POG and a Flanger flavour of some kind: Electric Mistress (does chorus too), Flanger Hoax or a Neo-Mistress.
Regarding brand parity, I'm kidding of course, but the suggestions are genuine.
Gregmon's suggestion for a Tech 21 chorus was on the money, too. As has been suggested, more info is necessary for better targeted help; maybe fill out your profile.
Good looking board so far, look forward to seeing it with new editions and all wired up!