Interesting chance for self-reflection... I tend to be logical and structured about my thoughts, but I do spring on tangents when inspiration strikes, and I am very visual when analyzing theoretical principles or quandaries.
I imagine that my mind would be heavily reminiscent of several science fiction franchises in setting - in fact, strike that; it would be the Warhammer 40K universe, seeing as in a vast galaxy, virtually anything is possible so long as it functions on existing house rules... So, any particular realm of thought or fancy would be represented by a different world or warp anomaly. Everything from idealistic principles and philosophy (places of learning and peace) to carnal desires and base wants (hive cities and Dark Eldar colonies) to the hustle and bustle of life and the struggles of modern man... And, of course, frequent mash-ups of other intellectual properties and concepts - hey, the Ruinous Powers of Chaos REALLY wanted to see what would happen if Desert Punk (anime) was set on Arrakis (Dune)! Or if Fight Club! were set on an Ork Rokk. Or if the Imperial Army mustered a lesbian stripper battalion! Anything is possible.
Except there would always be background music, piping in from seemingly nowhere. And it would frequently be metal.