As it is, UBB is already pretty devoid of extraneous info and graphics.
One thing I can think of off the top of my head is to disable posting icons & signatures in your General Settings. The styles can be edited in the Style Settings link in the Control Panel - just decide on the color scheme you want and insert the colors where applicable.
Aside from that, you'll have to be more specific as to what your definition of "unnecessary information" is, so we can give you a more accurate method of removal.
---Skorpion
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This just in: the New York Police have just apprehended the person who let the dogs out.
