Let me show you something.
This screenshot was not part of my first ever map, but it is pretty darn close to it.
In the simplest of terms; it is shit. There are no light sources, but there is light, not even a boxlight. It is heavily unfilled, could have some particles, some torches, perhaps some corner walls, fog, dust, decals, clothes, books, paintings, ornaments, a skylight... ANYTHING would make it better.
Now look at this screenshot: I was going to use it in the Three Week map challenge we had about a month ago:
It's not excellent, but it's better. It relies on a dark boxlight, some pointlights, small light sources, light ray billboards, some distinct features, lots of ornaments, decals, some particles (flies near the tipped over bucket), curved walls, emphasis, hierarchy...
That first map probably took me around 1 hour and maybe a bit more.
That second one, took me 2 days. Because I wanted it to be great, but, I wanted it to be something I was very proud of. Using similar techniques, I came up with a slightly more empty room, because I discontinued my entry, but I at least tried to use the same methods, and that too, took me 2 days.
Maps don't happen just like that, and that's what's the most memorable when people review Amnesia. They don't focus on the story, or scripts, but the maps. How they can be so immersed into the game by the environment is the greatest, and if you can accomplish this, only then will you get a good mod.
Sorry about my rant, but if you consider it from someone else's perspective of starting out mapping, you'll realise how tedious of a task it is to get it 100%. Start off small, gain confidence, make a good map, take a screenshot, send it to the appropriate thread, ask for criticism, improve, then repeat from gain confidence.