@ Gan: RMXP Vs. Xtremeworld.
@ Gnome: If you have Photoshop, set your grid settings to 32x32. Then the images will snap into place as you drag them across the screen. I'm using this method for the new Roguesoft tileset. Here's how to change your grid settings:
In the finder bar, select Photoshop: Preferences: Guides, Grids & Slices. That'll bring up a window with your grid settings. Make a grid line every 32 pixels, (assuming your tiles are 32x32) and set subdivisions to 1. You can set Color and Style to whatever you want, I use Light Grey Dots myself as you can hardly see them. Click OK when you've chosen your settings, and then View: Show: Grid to make your grid show up.