I'm going to attempt to critique this map visually. There are plenty of other elements, such as game play and optimization, but I think I'll do my part just for the sake of visual appeal.
Here we go!... (The explanations will come before their respective pictures.)
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This section seems overtly empty. It simply is just too much space for nothing. It would be too easy for you to add some kind of brush structure, or even some large static props.
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Props such as these look better if you turn off their shadows in their flags.
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This section seems like it could use a better texture for the ceiling. Sure it makes sense that an entire shed like that could have nothing but corrugated tin covering it, but in this case, for a map, it could look a lot more interesting (perhaps a different color?)
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Another bare spot, but this time you attempted to fill it in just a little. Well, this brings me to another point: Whatever you put to fill in the space, it needs to be meaningful. Case in point: that transformer doesn't seem to be connected to anything (those lamps look like they could use a dangling wire). Sure you could imagine that it's all laid underground, but what fun is that? (Not very appealing in my eyes.) Besides, a place like this doesn't seem like it's nice enough for underground wiring.
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Reflective pieces such as this wouldn't look white like this if you placed cubemaps in your map.
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Is this a bathroom? If so, I would think it make much more sense for the utilities to be placed on the walls. Rather than be strung about on the floor. Best way to do this so that they can still be picked up is by checking the flag "start asleep." That way, a player won't get caught on them when their running away for dear life.
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The shelves from these grocery kiosks need a better texture for their cap; it just looks too weird to not notice. Another thing, this particular turned-over shelf seems to be floating above the ground. Might want to fix that...
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The door to the left of that breaker box leads to a dark short dead end. I think this makes a perfect opportunity to add some kind of surprise there to reward the curious player; health or ammo of some type. Another thing: There is a complete lack of doors in this map (except for the rooftop). Any open spaces are just that: open spaces. No doors to keep the elements out. If you were to add doors, they need not be open-able, just make some brush-based doors that remain static and stay open all the time. Just something else to think about...
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This spot reminds me of some kind of freezer or something, but it is very ill defined. The combine textures remind me too much of HL2 even though I think they were being used here purely for choice of interesting metal. Another question: Is that room in the picture supposed to be some kind of display case? Or refrigerated kiosk?
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This room would be just a little more interesting if you had glass in these windows. This room, the hallway and the diner all suffer from this.
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This section of the room is too noticeably dark. Even if it was that dark, which is o.k., I would suggest adding some light sources turned off (or turned on...).
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Here's a place where the shadows should be turned off IMO. Fences don't normally cast shadows like that, and you would be better turning theirs' off.
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Normally, gravel doesn't pile with that sharp of edges. I think you should round them off a bit.
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Another bare spot...
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The picture may be a little too dark to see, but there is a weird shadow cast by the displacements. Not sure what's going on there.
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This a very barren place to be. It's not pictured, but you have one lonely health vial sitting in the corner. This rooftop deserves much more.
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Some other things I didn't feel the need to post pictures for:
The road coming into the gas station stops at the cement. Couldn't you define the road all the way to the entry gate?
There are some other barren places indoors as well. I don't recommend placing too many props that collide with the player because they tend to get in the way, rather than provide Gravity gun ammo.
The environment is not totally believable IMO, but good layout nevertheless. It is a map that could use a bit more detail but is way better than most entries for a first attempt! Good stuff; can't wait to see the progress on this map!
