On this page you can find introductory information about how to care for the photographs and paintings in your collection.
From the Illinois Collection Preservation Network, a two-part webinar on caring for and preserving photographs and still images.
The Smithsonian Museum Conservation Institute defines a painting here and offers this guide about why paintings change over time and some basic preventative and protection measures. They also wrote a guideline for knowing when your painting needs to be cleaned and what it means to have a painting restored. This page discusses varnishes on paintings. And, lest you get too confused, they offer a handy glossary of conservation terms relating to the care of paintings.