First off, make sure that your program can save areas of the image as transparent. This is very important for the finished look. As far as I know, the stock MSPaint program that comes pre-installed on computers using up to Windows 7 does not have this capability.
Second, the program must, at a minimum, be able to save the files in a PNG format. This is the format that DCR 2 uses.
And third, it must have the ability to save the files in specific pixel by pixel sizes, the sizes depend on the item you are trying to make a skin for.
Vehicle:
Frame - 202 x 100
Seat - 130 x 130
Wheels - 105 x 105
Driver:
Arm & Leg pieces (2 each) - 100 x 70
Head & Body- 100 x 80
These are the minimum requirements, the program you pick may have more capabilities, but it needs at least these 3 to work with DCR 2. There are many programs out there, free and purchased, that can be used. The program you decide to use is totally up to you.
Edit: There appears to be a name size limit to what DCR 2 can make use of. If the file names are too long, it will automatically truncate and only use the beginning of the file name. This may have unexpected and unwanted effects including unwanted skins being applied to more than one item. I have noticed this happening on wheels during skin design and testing.
These are the basics, and should be enough to get you started. Have fun!
