This is going to be my attempt at the quickest edit/critique ever. Generally, with these expectations, I end up going way over the top, but hopefully that's not how it ends up, because I really want to go to sleep.
This is my edit. Helm was pretty much spot on with his musings, and I don't want to undermine his edits/critique in any way, as I think he did an excellent job interpreting what you want to accomplish. With that being said, I offer my own interpretation of what you have set out to accomplish. I've made a ton of brick tiles in my time, and so I've become very accustomed to creating them in a specific way. That way happens to, in general, be a happy medium between what you've done currently and Helm's edit. It really depends on the scale of the brick, but the average tile I make seems to fit between yours and helms. If I were working on 16x16 tiles for a building that is about 4 tiles high, I would 100% use a method that is extraordinarily similar to Helm's; maybe shrinking the vertical height of the bricks a bit.
Anyway, as hs AI had pointed out earlier, your tiles have this nes vibe to them. That's not necessarily a bad thing, but to be honest, I don't think that's really what you were going for-- correct me if I'm wrong. So, aside from equalizing the spacing between each brick, the first thing I did was deduce why you're latest tiles (which are markedly better than your originals) still carried that nes vibe with them. A lot of it has to do with contrast, and just as much has to do with your understanding of color. While your new tiles do an excellent job of clarifying the singular bricks, they don't really achieve much as far as the portrayal of an actual brick. This has a lot to do with the consistency you carry over from brick to brick. When you are attempting to break up a grid -of any sort- the first thing you want to do is break up the grid of the initial tile. If you can look at a tile and observe a grid within it, then you've already failed and need to address that first. This is a natural process in creating tiles, and only experience will give you the know-how to destroy the grid before it starts. To elaborate on my primary points I would like to point out that minor discoloration between the bricks is a fantastic way to destroy the initial grid. Helm does a wonderful job of this in the tile that you see between the two windows, and he does a pretty good job of this with the tiles outside the window. Although, it is important to note that he breaks the grid with texture, as opposed to coloration, with the bricks outside the two windows. Even more important to note, is that while he defines this differentiation with texture, the end result is still based upon value. The number of indentations/scratches on any given brick will determine its overall colorization. A heavily marred brick is just going to be a darker brick to the untrained eye. And even the trained eye to some extent: even though I know what to be looking for, if I were playing your game I would not be critiquing the texture from brick to brick as I chop off the heads of enemies. To finish, I would like to point out your choice of colors.
While I think the colors you started with are miles beyond what you started with, I think you could do a much better job with them. Understanding colors is a very difficult job, especially if you use video game references as an applicable guide toward choosing them, but it's not beyond anyone's grasp. To reiterate Helm, I probably would never choose the colors that I have if it weren't for this edit. But, I did what I could to maintain the look that you were going for. The end result was the vibrancy you had in the beginning, combined with the very subdued bricks that you ended with. I introduced a 7th color that was very similar to the base color of the bricks in order to break up the montonoy from brick to brick. It would be safe to say that the 7th color was a secondary primary color of the bricks. It's really quite subtle, but the amount that it accomplishes when you spread out the tile over a large expanse can not be questioned. Obivously you have noticed that the mortar between the bricks has taken on characteristics from your older tiles. This is just a general preference I have, as I find that a divider that contrasts with what you're dividing does a better, and more predictable, job of breaking up the grid. In addition to that, it also does wonders towards adding depth to to everything. Regardless of that fact, it is not impossible, nor improbable, to achieve what I have with a mortar that matches the colors of the bricks. In fact, if I were to share colors between the mortar and the bricks, I could define a level of realism with the bricks that I currently can not. It's really a question of the style you are going for, and in your case, I assume you're going for generalizations and cartoony appearance over realism. I realize that I didn't really go over anything concerning color choices, and instead focused on a few random theories that revolved around color choices (specifically: value), but there are numerous things you can read on color selection, and not so many things you can read about color theory. Especially when it comes to brick tiles.
For all that I've said, I feel like I could write another 2-3 paragraphs, but I'm going to end it here. If you have any further questions I would be glad to answer to them.
