In general, most paint programs do not support Unicode. They simply are non compliant to Unicode, and hence can't display Unicode characters correctly. Gimp and latest version of Photoshop does support Unicode, but the supports in these programs are very basic, and raw. Working with Unicode characters such as Indic Hindi in these paint programs is not an easy task.
Now, this problem is solved. The freeware paint program called paint.net is here to solve your Unicode character-paint-program problem. You can do all kinds of fancy Unicode-character-paint manipulation through this paint program. Paint.net works like a scaled down replica of Photoshop, and had all kinds of advanced tools such as filters, plugins, layers and unlimited undo-redo. And, above all, it is very sleek - only about 5 MB download. Though, for this program to run, you need Microsoft .net framework -2 installed in your computer.
Here is some sample - Hindi word KAHANI had been manipulated through some built in filters - you can do infinite manipulations by combining them!
Download paint.net from here