I think there's an issue that you're detailing the tiles rather than the scene.  If this set is for a bar/pub/tavern/inn, or really any setting, try thinking of things that can go in it to add interest without adding pixel noise.


For instance, when I think of a pub, today or way back (for some reason I'm going to the late victorian era with your palette), I come up with:

walls:
* narrow front windows across an entire wall, or nearly so.
* routinely built on a corner-lot, for 2 walls of windows.
* a nook or two
* shelves with bottles
* photographs, papers, advertisements, and other flat memorabilia
* soot from cigarettes, cigars, and in old times kerosene lamps or even candles depending - concentrated near the ceiling.
* tchotchke
* heating. these are warm places.  a hearth should be found somewhere in any bar built pre-war, even if it's closed up.
* coathooks and hathooks, generally under the counter in front of the barstools, as well as by the door.

floors:
* boards stamped and pounded so hard you can only tell the cracks if they've been replaced or are otherwise a different color from the boards next to them.
* pits, stains and scratches more visible than cracks or wood grain.
* Straw and peanut shells on the floor - a necessity, grouped under furniture and in corners.
* if there are cracks, they're actually lighter than the boards, because they're filled with pulverized bits of the above.
* a particularly smooth, ashy ring in the largest standing area or most-used path of traffic.
* tobacco stains everywhere

I can imagine a very engaging bar with very little texture/noise and even just half of these things.  don't spend so much time on individual tiles, spend time creating an environment and then detail if you still feel the need to once that's done.

Be careful of your perspective lines.  You've got a lot of things approaching straight horizontal.  in this perspective, though that's generally forgiven and you don't have much space, you really don't want to get more shallow than 1/3.

Also take a keen eye towards body language; females should be obvious from pretty far away even without details.  lastly, watch your shading methods - you don't want the female shape, though it's more complex, to become significantly darker than the male.

Here's my attempt at guiding these points, see if you like anything that's happening :

DO NOT I REPEAT DO NOT USE THE PIXEL-ZONE ISOMETRIC TUTORIALS.

Whoever wrote them does not understand 2:1 isometric fully.  he loses a lot of compression in places, and gains some in others.  the square on which he defines the circle is not actually square, invalidating his form.

a real vertical square will end up about 88% as high as its undistorted width, or in perspective close to 125% of the distance covered (so if your tile block is 32px wide, then the height of the cube should be 20 pixels, *not* 16).



Here are some common cube sizes drawn in this method:



The astutue will notice that this is not 100% accurate - the value is actually a bit less than 125% (true ratio involves an arctangent), and the higher sizes should estimate accordingly - 1 pixel less starting at 32.  However, I keep the 5:4 method, as this ensures that all smaller cubes can tile on themselves to line up precisely with the larger ones, and that patterning can be achieved with relative ease.

keen observation is needed, and simple math (like 4*4=16 kind of simple).  the eye generally knows when things are off, even if finding what's correct can be harder.

precision is a given - if you place single pixels, you are precise, if you do not, then you're not making pixel-art.

drawing quality and projection accuracy do require practice or technical knowledge, but this can be picked up through any of the numerous tutorials or, for those really interested in an academic sense, books on the subject.

but no, you don't need to be a draughtsman to make a decent building.  looking at what you're doing, paying attention to others, feeling what is right and what isn't, these are the most key.  

for instance, if you have a particular question about a piece of pixel art, such as how to space these windows, posting in the appropriately-labeled "Pixel Art" section of this board is the best way to begin!