Is it possible to continue to work on a new location indefinitely?
When do you say enough is enough with the clutter and the lights and the FX etc etc etc... ?
Furthermore, do you think each environment you make *needs* something distinctive? Be it a new texture or new object you've made. Is it enough to stick with the default objects/items and just try and be creative or do you feel the need to go above and beyond by making new textures and new models to replace existing and otherwise, (seemingly) repetitive, things.
Doesn't it depend on what your mod is intended to achieve? I'm in the process of creating some interiors at the moment, but their purpose is to tell a story, or part of a story. Once I have enough NPCs to allow the player to investigate the story, and to provide a bit of atmosphere, and once the interior contains all of the necessary clutter to match the story, it's finished, and I move on to creating the dialogue and quest elements. The story, in other words, defines what I need that location for and what I need it to contain. I'm adding some new objects, like re-textures, to spice it up a little and catch the player's attention, but I don't think they're vital to my mod (which is just as well since my artistic abilities are limited, to say the least), they just add a little colour to the story. On the other hand, if the location you are creating is the actual purpose of your mod - like a new player house, say - then new elements are probably more important as you'll want to make it stand out from the crowd of other house mods.