GeoServer - how to show image

Hello to everybody, 

For my job I have to use a map server and I choose geoserver, I find it 
really amazing good, and also the documentation is great.
I installed it without any problem, and I made it work with data from 
shapefiles and postgis db, but now I want show some image. I was looking 
for same tutorials to do it, but still I don't find theme.

Please some of you can help me. Really Thanks.

Regards Antonello.