I have developed cross-platform software that may help you with creating terrain tiles for two-dimensional tile-based games. Its called The Tile Wizard. The Tile Wizard was designed for the main purpose of testing your tiles to see how they look together as they would be in your game.

The program is being constantly improved.

Find updated information at http://www.twodimensionalgames.com

Tile Menu:
 ID - Shows the Tile's number out of all of your tiles. Clicking this button selects this Tile as the active Tile.
 New - Clears any pixel drawing made to this Tile and erases its stored history.
 Load - Load a .png .bmp .gif .jpg or .jpeg image to work with.(You must load an image of the size you specified at startup)
 Save - Save your Tile as a .png .bmp .gif .jpg or .jpeg image.(Saves the image as the size you specified at startup)
 Grid - A grid that overlays a Tile area if you want that feature turned on for that Tile.
 ANIM - (Animation Sequence) - Create an animation sequence within this Tile. Placing this Tile in the Tile Tester's Override Mode will cycle through the frames of this sequence(using the specified delay values) where it would normally be displayed. Holding the control key down and clicking this button will remove the Tile's animation sequence if it has one.

Tile:
 Allows basic pixel editing of tiles. Edit tiles at a 1000% zoom level.
 Undo pixel - Undo as many pixel markings as you want until you reach the beginning of the active Tile.
 Redo pixel - Redo pixel markings until you are at the most recent action on your active Tile or until you draw a new pixel.

Tile Tester:
 Default Mode - See tiling of your active Tile in an 8x6 tiled area.
 Override Mode - Place custom tiling of any of your opened tiles in the same 8x6 area. Now supports Animation Sequences.
 Default and Override Modes - See the editing of your tiles instantly take affect in the Tile Tester.

Real Size Display:
 See what your current page's tiles look like at a 100% zoom level.

Color Creator:
 Color Bar - Shows a horizontal bar of each possible R, G, or B color one pixel wide for each hue.
 Value - Each R, G, or B Color Bar has its numerical value displayed to the Color Bar's left.
 Slider - Slide the vertical bar onto the desired R, G, or B value.
 Set Palette Color - Click this solid colored rectangle( R, G, B Color Bar values combined ) to set the selected Palette Slot's color to be this color.

Palette Menu:
 New - Clear any customized colors and start from a blank palette.
 Load - Load a saved Palette from a previous session. Also loads your previous Color Quickbar.
 Save - Save your customized Palette and also your customized Color Quickbar.

Palette:
 Customizable color Palette with 256 Palette Slots.
 Copy a Palette Slot to a different Slot by dragging a color to a new location.

Color Quickbar:
 10 Color Quickbar Slots to quickly change color while editing your tiles. Accessable with your keyboard's 1-0 keys, - and = keys, and the keyboard's numberpad.

Color Grabber:
 Hold the control key and left click a pixel in your Tile to place the selected pixel's color into the currently selected Palette Slot.

Custom Tile Size:
The program now supports a custom Tile size. You can enter a custom width and height during the program's startup. The size must be: an even number, greater than zero, and less than sixty-five.. Only one size may be used per instance of the program.

More tiles:
 The program is not limited to four tiles anymore. You can have as many tiles as you need to work with using the Back and Next buttons.