When you're looking for images for a design collage or for research, you want to make sure the resolution of the images you find at least 1000 pixels in one direction. Most of the time this will ensure that it is high enough to project, print, or use later in your 3D model.
Usage Rights
When designing for a theatre company it is important to pay attention to the usage rights for images you might use in your final design. You'll do well to familiarize yourself with Creative Commons licenses.
Under the tools menu in a Google image search there are features that allow you to filter for high resolution (large) images, and by usage rights (Creative Commons licenses).
Stock Images
Another good way to find high quality images (and this is usually my preference) is to search royalty free stock photo websites.Here are some sites I use most.Lost and Taken texture gallery and texture lovers are good for textures and are also free.Storyblocks.com Has photos and video as well as music and effects. Requires a low cost subscription but has lots of good material.You can find great images on sites like istockphoto, which has good images that you buy for $12-33.
For specific period images you can search the Library of Congress Prints and Photographs Online Catalog or the Life database hosted by google images.
Video Footage
Storyblocks.com Has photos and video as well as music and effects. Requires a low cost subscription but has lots of good material.You can find great stock video footage at istockphoto and Getty images, but you can expect to pay somewhere around $50-$100 for a clip.
