Please, please do change the eyes away from that generic cute anime-rpg thingie, it really doesn't fit the Terrans in StarCraft any... AT ALL. They're rough guys, they smoke, the swear, they're dirty.
Apart from that, the Space-Marine looks better with the new colors. For the Siege-Tank, I'd advise you to study more reference material (both from the first and second part currently in development) - that is, if you want that tank to actually be a Siege-Tank. It just looks way different design-wise.
Can't comment on the tiles. What do they represent? Sand? They are not readable in the slightest, try thinking more of a structure behind the shapes and not of the shapes themself (ie. try drawing/shading little stones or whatever, don't draw random lines and dots in a way them seems nice when zoomed in).