If there is one thing I let dominate a map's design, it usually is the environment. I'm less interested in creating maps that are strictly "good" and more interested in creating maps with a unique identity, and letting the environment drive layout decisions is a great way of doing that. I can usually derive some larger organizational scheme from the environment that then helps drive both the large-scale and small-scale layout design decisions.
For example, Steep has a train line that runs through the entire map. The train does not function and serves no actual purpose in terms of gameplay, but it helped guide the design of the rest of the layout. There are three distinct outdoor areas, and each one responds to the train line in a different way. Restrictions breed creativity and all that.
(You can see some of this thinking in Valve's maps as well. On Mercenary Park, there is one continuous steel truss structure that runs through the entire map, lining up all three control points. All five of Well's points line up exactly, and Granary's points are almost all in a straight line, with the final points nudged 64 units to the side. Dustbowl, Goldrush, and Upward are all designed as inward spirals. These organizational schemes don't always come strictly from the environment, but they do help reduce the possibility space you design within while also organizing the map in a way that feels more architectural/"real.")
(Also, check out how Spectre's red spawn is designed. Good shit.)
Setpieces also help in this regard. What does it mean to place a control point on top of a large tower? On a helipad overlooking a cliff? Dumping a payload off of a cliff onto a UFO?
I should also add that these organizational schemes and setpieces aren't things I set in stone from the start. Often times I just start building a small gameplay space and discover later where a larger thematic element can fit in. In Snowbase, there is a pretty strict relationship between the final point and the blue spawn directly underneath, and it would seem that it drove the design of the rest of the map - but the first part I started making was the helipad. Everything else pretty much fell into place when I decided to curl the layout around the helipad in order to break up sightlines.