hsetroot is a tool which allows you to compose wallpapers (root pixmaps)
for X.  It has a lot of options like rendering gradients, solids and images
but it also allows you to perform manipulations on those things or chain
them together.  You could, for example, use one standard background image
together with tint to make it fit your current theme.  It is also compatible
with semi-translucent applications like aterm and xchat.

At the moment, hsetroot can render: gradients (multi-color with variable
distance), solids (rectangles) and images (centered, tiled, fullscreen, or
maximum aspect).  It supports the following manipulations: tinting
(overlaying a color mask), blurring, sharpening, flipping (horizontally,
diagonally, vertically), and also allows you to adjust brightness, contrast
and gamma-level.  At last, it supports alpha-channels during renders.