Okay, so there is new version of the editor, now fully functional. See the first post. Noone has downloaded the previous one... nevermind. Feel free to report bugs and suggestions.

The stones look out of place, almost like teeth growing out of the ground.

Yeah, that's what I wanted. For now there are no updates regarding the tileset itself. Anyway, thanks forthe tips EvilEye.

I've been recently working on a game, and I made an approach to make a tileset right now. Here it is.

C+C please. I'm aware of some issues by looking at it now, but It's too late to fix them. Maybe tomorrow. I'm also working on a simple Map Editor for my future games. For now all the tools are working besides the History system. It supports 64x208 tile sheets with 16x16 tiles. You can download it if you want, and you think it may help you test your tilesets. There are some known bugs but feel free to report.

Small documentation:
The config window should be self explanatory but there must be told that you should write all the names (Map and Tileset name) without the extensions of the files.

Tools:
Brush Tool - simply pick it up and draw;
Marquee Tool - use to select a rectangle;
Cut Tool - cuts selected area;
Eraser Tool - use it like the Brush Tool;
Copy Tool and Paste Tool - to use Paste you must first select area and press Copy button. After choosing any other tool, the Copy Tool will be released;
Move Tool - use to move selected area;
Crop Tool - use to crop the map after selecting desired space. It won't work if the selected area is smaller than the screen (edit space).
Undo and Redo doesn't work right now.

Use arrow keys to scroll.

The Knight uses too many colors, or rather doesn't look like he's been made with that much. I noticed you sometimes even use a color only once in a whole image. You should get rid of some colors or make a better use of them. The lineart is very unclean (In both pieces).

As for the old man (is it?), you should work on your anatomy skills because he doesn't look like a human in fact. The shadows seem randomly placed, and sometimes you even use black dither instead of shadow tones avaible. The background is too dark, and try not to make trees  so linearly placed.

A teraz po polsku .
Zdecydowanie w rycerzu użyłeś zbyt wiele kolorów albo po prostu niezbyt dobrze wykorzystałeś te, które wybrałeś. Zauważyłem, że czasem nawet używasz koloru tylko raz na cały obrazek. Powinieneś pozbyć się jakichś kolorów, albo zrobić z nich lepszy użytek. W obu pracach kontur jest strasznie nieczysty - nie używaj "schodków" do rysowania ukośnych linii.

Jeśli chodzi o tego starego faceta (a w ogóle to jest facet?), powinieneś poczytać trochę o anatomii, ponieważ on wygląda jak zgarbiony o ile w ogóle to człowiek. Cienie wyglądają jakbyś je umieścił losowo, a czasem zamiast dostępnych tonów średnich i ciemnych, używasz czarnego dither'u. Tło jest zbyt ciemne, a drzewa nie powinny być poustawiane w rządku.

Copying and pasting stuff isn't the best way to improvement. You didn't even manage to merge some colors that differ a bit.
I had my edit for you, but when I saw what the others did I considered it being useless .