You might want to take up programming. It's fun and rewarding (and it can prove a good source of income as well).
The Gnome Developers' site
has a lot of good content regarding programming Gnome, including the programming guidelines
, but if you are new to programming it might be a tad steep. Creating your own themes - like GTK themes (application interface themes in Gnome) - is a lot easier to get started with. Check out art.gnome.org
for some examples.
And if you want to get started with a good programming language to get real stuff done (rather than moving around bits in memory...), look into Python
. There are several good free books on getting started with Python programming, most notably Dive into Python
and my choice, A byte of Python