Grab your ordinary barstool. It's most likely covered in a clear coat or sealant, so take your sandpaper and sand it away until it has a more dull, matted finish. This will help make your paint more effective, and last a lot longer.

Think of how you are going to decorate your stool. For mine, I took an old German bible I had sitting around. The pages were very thin and fragile, so I carefully cut out a section of the book.

Next, tape off all areas of the stool you do not wish to paint.

Brake out that black acrylic, and go crazy!
I'm one for instant gratification, so I like Acrylic paints because they are long-lasting and fast-drying. :)
For almost all of my projects, I break out my hairdryer and dry that paint even faster. (If you do this also, make sure you put the dryer on the "cool" setting very last, to help the paint set.)

Once the paint is dry, rip off all of the taped areas.

Use mod-podge to create your design. Make sure you use the paste on the bottom of your image as well as the top, to prevent any bubbles or future peeling.

After I glued pages onto the support-sections of my stool, I realized what a horrible idea it was. :-O

Time to paint over those....

And there we go. :)

Apply your clear-coat or finish to the entire stool, and let it dry COMPLETELY before using it.