Me, personally, I'd like to have a few different "Templates" of sorts. Exteriors that are implied or actively shown to be part of your base. So if your base is underground, it might look like a City of Heroes base. No windows, nothing but internal lighting. If your base is a building, it might have a small exterior when you access it or windows that show a fairly generic cityscape. If your base is in space, well, just have a single direction that shows the Earth or some alien world. Bonus points if the direction changes slowly over time based on time of day.

Altogether, I want bases to feel integrated into the world. Not just some closed-off pocket dimension being the one and only choice.