Seems you got a lot of thougths on your icons, but none for your environment stuff.
For my edit I chose your anvil, but the principles should also help your other environment pieces, since a lot of the stuff I am pointing out can be applied 1:1 on other graphics.
It's not really palette-restricted pixel art, rather low res digital painting, but yeah, no problem if you want to go for that (Tibia has pure pixels - saw some stuff on PJ and that kind of style - I dunno).
The underlying forms and proportions you have going on are pretty solid. The peak of your anvil seemed a bit detached (to wide at the left) and wrong in terms of perspective (the straight line looks nice there, but is construction-wise off) - I suppose this is more a matter of taste - I just adressed it since I remarked it and applied it to my edit.
What's actually really bad are the internal lines
I talked about internal lines here:
http://wayofthepixel.net/index.php?topic=16261.msg148111#msg148111(example number 2)
You should avoid them if possible, since they really easily destroy the form impression of a drawing and rather go with contrasts -
It's ok to use them if you have stones with gaps when the line illustrates a shadow (like at your street tile those shadows are missing).
You just shouldn't illustrate boarders with dark lines. Someone mentioned that looking at an edge of your room helps you to understand that principle.
The next thing which isn't solved optimally is that the top and side plane are in terms of value pretty similar (shows up once you remove the internal line). The light seems to come from the side (brighter than the frontplane) and the positions of the highlights confuse the lightsource further (front one at the peak seems fitting, rear one at the knob seems to come from the left side) - that's bad.
All in all the anvil seems to be to bright for the material - it rather looks like platinum, than iron or steel. The ones I know are significantly darker and look somewhat like this

If you study it you will see that there isn't a lot of saturation, the highlights aren't that bright and that it can get really dark.
I applied this observations and some small little details (like the form of the base and the hole at the top plane) in my edit and also changed the direction of the light from the side to the front - why that?
If you are going to add an additional cast shadow which will anchor the graphic in the surrounding environment I suppose that this angle for the light direction is one of the best options you have (I just went ahead that the top plane is brighter than the side planes - sunlight, ceiling lamp?).
Can't say for sure if it's the best direction for cast shadows which will be casted from-the-object on-the-object as well.
Read carefull ythrough all points and compare my version with yours

Do you see the big differences:
That your anvil seems to be floating?
That your anvil has a weaker form?
That your anvil seems to be to bright?