The number one problem with building a thing out of doodads not designed for "building" is that one is limited to the type of item (doodad) one can use to build a structure like this with.
You could have (still can as an addition) use the Icecrown Walls (under destructibles) at the ground level to build the pillars on.
I believe you can match pretty close this icy shade of blue with the city scape "white" doodads, like the arch.
I got a close match without fiddling too much. I changed the colors to
Red:100
Green:120
Blue:210
See the picture attached below, the bluish arch is in front of the white version, Icecrown stuff below it.
Anyways - if you fiddle with the coloring I would bet you would get a lot closer than I did in a couple of minutes of copy/paste and a few quick color adjustments.
That would open up a few more doodads for you to work with with the icecrown set.
I tried it with the sunken ruins wall, the green bits throw it off - but I would assume that with a little color adjustments you can "frost" a lot of the doodads from other sets.
Try experimenting with Human units too and the cathedral both get fairly close to that icy color with the three numbers I gave you. I gave it a go with the guard tower and the scout tower - set the team to gray - the gray goes real good with the color theme.
All of this should give you enough variations in models to break up the the monotany a bit. Say use the Scout Tower unit for team gray (sorry if you use the model for a doodad the top switched from scout, guard and other towers) Remove its pathing, make it a flying unit with a specific height so it will be where you want it.
