EMAN2 includes a good selection of test images. They come in many shapes and forms, from simple gradients and shapes to basic noise models. To create a testimage start by running e2.py, and creating an empty image that is appropriately, for example as follows: 

#] e2.py

Welcome to EMAN2
Prompt provided by IPython
Enter '?' for ipython help

In [3]: e = EMData()

In [4]: e.set_size(256,256)

Then issue of the command embedded below in the table to generate the pixel values

attachment:xcoord.png

attachment:ycoord.png

 e.process_inplace("testimage.gradient")

 e.process_inplace("testimage.gradient", {'axis','y'}) 

attachment:axes.png

attachment:circle.png

 e.process_inplace("testimage.axes")

 e.process_inplace("testimage.circlesphere") 

attachment:scurve.png

attachment:gaussnoise_large.png

 e.process_inplace("testimage.scurve")

 e.process_inplace("testimage.noise.gauss")