Forerunner objects?

Have you looked at the items available? Just about every object is "forerunner style".

 

try looking at images of forerunner architecture from past Halo games,
and then try to mimic it in your map.

most of the pieces available in Forgeworld are Forerunner themed,
but you still have to build the architecture yourself.

 

Google images is your friend here. Check out the architecture of past games... I just google it all.

 

I can go ahead and tell you that Right angles are not very forerunner friendly.
And actually, a map with almost no right angles could be really badass if done correctly, I think.