I replied to this in the N&R section, but then saw the thread had been started here. This thread covers quite a few different options for terrain:
https://www.dakkadakka.com/dakkaforum/posts/list/751316.page
For my Epic/
LI I have gone for a real mix of terrain types. Rather than just have a 'city' board or an 'urban' board the scale really gives you an opportunity to include multiple areas of terrain. Not only does this make the board look a bit more interesting, but it gives some tactical variety, and I think makes the narrative a bit more engaging. As a final point, it is also a little reference to the way terrain used to be arranged in the old Epic battle reports
Sorry for incoming photo-spam!
These are some of the classic (30 years old now!) Epic buildings. I cut out 'city' areas from a cheap PVC gaming mat to denote city and industrial areas, rather than just having buildings sat on grassland, and have these connected by roads - which gives more tactical options.
This is a mix of the official
GW Adeptus Titanicus terrain, with some scatter bits from Vanguard and other locations, and I added some little dioramas. The train and tracks is from Grimdark terrain.
Assuming forest terrain will work in the same way in
LI as previous Epics, I put down an 'area' for terrain and they you just have these little model railway trees in between, so you can move forces about in the forest as necessary.
For further variety, and useful things to put objective markers on, I added some ork villages and farms (although appreciate this won't be useful for
LI immediately, you might then take the 'blessed path' and move on to Epic!
Finally a complete battleground shot (sorry is taken from a website and not my photo) that shows how all of the areas fit together. Hopefully should give some food for thought, making terrain for that scale is so much fun because it lets you do lots of things you can't do at 28mm scale, so hope you enjoy it!