Little photographs on visiting-card or calling-card-sized backs are called
"carde de visitas" or "CDV's." I'm not sure of the spelling.
The came into
use shortly before the Civil War.
A highly-silvered or mirror-like image on glass is a daguerrotype, the
earliest type of photograph. They came in around the 1840's.
Images on glass in boxes are usually ambrotypes. I believe they are
negative images on glass but they have a black felt peice behind them that
makes the image appear positive. I believe they came in shortly before the
civil war.
images on dark black metal are "tin-types." People often assuming they are
the earliest type of image, but they came in about the time of the Civil War.
I have had very good results with an older 35mm camera and a set of three
overlapping screw-on closeup lenses that I bought for $15.00. But it seems
like scanners are very popular these days. Apparently very good ones can
be had for very little money. And good software can greatly improve the
results.
There is a lot of information on photographs at
http://www.CyndisList.com/photos.htm