What about a non-portal themed map + timetravel?
Ah, someone mentioned a map "time arch", just checked it, the creator came up with the similar effect, when the portal emerges from the floor. Trust me, I never played that map! 
Mine is hidden because the scientists wanted to hide it, and it can be activated from a sealed nearby rom (will be that way in the official map) and in the future I also plan a "fixing puzzle, where it stuck halfway because of a panel, that needs to be activated first. Basically a map where you also need to fix the puzzles (like a maintanence worker) before u can start actually solving the room...
PS: if anyone tries the testroom, when u activate the portal (2nd button) u also experience a lag/hang in framerate and a small lag in the music?
Yes, I get that.
Only the first time I do it though after starting portal. If I just restart the map, it doesnt do it a 2nd time.
So is the time traveling device going to be a portal or a machine made from props? I made a time traveling map once (Aperture Time Testing Center) in case your interested in ideas.
My Work
[spoiler]Maps:
Revenge of the Angry Turrets
Capture the Cube [Co-op]
Capture the Cube 2 [Co-op]
TPWEGTH Sample Map
Aperture Aquatic Testing Center
Aperture Aquatic Testing Center 2
Aperture Time Testing Center
ML's Halloween Trick - 1000 downloads!
ML's Halloween Treat
ML's Combination - 1000 downloads!
ML's Jailbreak Labyrinth
ML's Tricky Teamwork [Co-op]
WIP:
"Capture the Cube 3"
Workshop Maps Link: http://steamcommunity.com/profiles/76561198008890579/myworkshopfiles/[/spoiler]
check the map at the end of my first post (small letters)
it will not be used for puzzles that require traveling back and forth, just mainly for transitions, traveling further ahead in time multiple times.
Anyway, the main question was about outdoor areas and maps with mixed style or with style not present in the official portal maps...
So it's a StarGate rip-off. JK, JK. That is actually a lot better looking compared to the one I made. Too bad it's not entirely puzzle related. BTW Is the Time Device showing the area you travel to? I'm looking at the rest of the room and it seems that the Time Device is showing a "future-ish" area.
My Work
[spoiler]Maps:
Revenge of the Angry Turrets
Capture the Cube [Co-op]
Capture the Cube 2 [Co-op]
TPWEGTH Sample Map
Aperture Aquatic Testing Center
Aperture Aquatic Testing Center 2
Aperture Time Testing Center
ML's Halloween Trick - 1000 downloads!
ML's Halloween Treat
ML's Combination - 1000 downloads!
ML's Jailbreak Labyrinth
ML's Tricky Teamwork [Co-op]
WIP:
"Capture the Cube 3"
Workshop Maps Link: http://steamcommunity.com/profiles/76561198008890579/myworkshopfiles/[/spoiler]
Everything I saw from you so far looks visually very pleasing. Your maps are top notch. Why don't you just do what you feel comfortable with?!
If you go with those who 'hate' this or that, you pretty much end up with a portal gun alone.
Mapping is about creativity. It needs innovative ideas to break repetitiveness and boredom. Slavishly adhering to themes and styles and preaching the Ten Commandments of dos and don'ts won't change that.
I have no doubt that most of us will enjoy the maps you come up with.
Keep it up!
Wellm I tought that portals should be round and not rectangular, and this one was the only model that looked nice. And yes, it shows the future, and from that future room,
But as I said, the gate is just a tool for transitions, will not be used to solving puzzles traveling thru it between times. The gate will be deactivated after a while after you entered it.