In general, it's possible to stencil over textured surfaces, however it depends on the roughness of your
texture and your desired outcome.
Some textures out there are really rough,
with huge "peaks and valleys" and if this is your case I would say
that stenciling may not be an option. However, there are light to medium
textures out there that are very suitable for stenciling. We have done many
faux frescoes for customers with our stencils and this technique actually
requires applying a textured plaster background first and then stenciling on
top of it. Of course organic stencil designs such as leaves and branches are
more forgiving than a designs that have straight lines and perfect edges.
textures it is especially important that you put very little paint on your
brush and always off-load it onto a paper towel. Use a rubbing/dabbing motion
while stenciling and try not to force the paint under the edges of the stencil.
You can also use a dense foam roller but make sure that you off load it onto
some paper towels so that it is relatively dry. Use very little paint and don't
press hard on the roller to avoid seepage. Using spray adhesive can also help a
to prevent seepage of paint under the stencils. We love Elmer's re-positionable
spray adhesive but any most re-positionable spray adhesives are fine. Always
make a sample first or try stenciling a small area in a corner somewhere and
immediately wipe it off with a moist baby wipe. Also, it's good to remember
that using high contrast colors (like black over white) is much less forgiving
than using colors that are similar to each other.