Wall art can be painted nearly onto anything you can
hang on a wall. Some artists even use aluminum sheets as
a painting surface to give life to brilliant works. The most
popular medias to paint on however are canvas, paper,
and board.  And by far the most popular paint used
throughout the centuries of wall art has been oil paint.
Oil paint has been around since the cave people!
Well, maybe not since cave people, but it has been
used for over four thousand years. It is the most tried
and tested media in all of art history. Artists can easily
predict how it will behave in various environments, how long
it will last on different surfaces, and can paint on a canvas
layer-upon-layer-upon-layer when working with oils.
The layering of oil paint requires a half-day
drying time for each layer painted, but this long process
permits a level of realism and detail no other painting media
allows. This is one of the reasons most paintings you see in
a museum are oil painting.
The other great media used by artists, which allows
for good definition and detail, is acrylic paint.  These
paints are considerably less toxic than oils and require less
ventilation to work with. They have a faster drying time, but
are much more difficult to layer.  Acrylics also come in
extremely bright and vivid colors; toning them down and
creating the color gamma desired for realistic paintings can
take years of practice.
Most of us associate watercolors with childhood
memories. But in the fine art world watercolor is a very
popular media among artists and veteran collectors.
Painting in watercolor is quite difficult to master because of