Ubuntu linux is rich with exciting graphics utilities, Here you can see simple but very useful 2D Graphics Design tools for Ubuntu Linux. Yes welcome to the fantastic world of ubuntu graphics.
Xara Xtreme, ( apt-get install xaralx) This is simple, easiest vector graphics drawing program. It is very userfiendly, it is very nice, which is not usual in this kind of applications.
Ktoon, (apt-get install ktoon) KToon is a 2D Animation Toolkit designed by animators (Toonka Films ) for animators, focused to the Cartoon Industry.
Synfig, (apt-get install synfig synfigstudio) Synfig is a powerful, industrial-strength vector-based 2D animation software package Beware you have to apt 2 packages: synfig (the application) and synfigstudio (the graphical interface to use it), so install both.
Skencil, (apt-get install skencil) Skencil, another good vector graphics drawing application. It has many clipart libraries included. Features like Bézier Curves, Transformed text and images, Bézier curves, rectangles and ellipses can be used as guides, Gradient fills, Blend groups, Writes EPS files
MyPaint, Although it lacks of layers, it is a simple but superb natural painting program. It has many interesting artistic brushes, and you can do your own. The brushes are pressure sensible , supports unlimited canvases, undo's making of it a very "living" and artistic way to paint. Download deb package from here dpkg -i packagename