yes, absolutely!

we will need a lot of in-game buttons with well designed icons of buildings, military units, technologies, orders... I can't even know all of them

and of course a couple of logos, or logo like in-game illustrations, like unit and building pictures (which of course can be made of their 3D model but 2D art would be better).

the project is still in an early design state, so I can provide mostly written information, and a project management site with some references on trello.com. just PM me your email address.