Listed here are image galleries that may provide photos for your presentations and publications. Be sure to read and follow the image use policies that are listed for each site.
UNL Image Collections (several categories available, search alphabetically)
This is a collection of insect photos taken by the UNL Entomology Department (credit UNL Dept. of Entomology). Several categories are available in the menu, including arthropod pests, museum pests, medically important spiders, etc.
UNL Entomology Flickr Page
This is still very much in process, but feel free to use any photos here (credit UNL Dept. of Entomology).
BOLD Systems Arthropod Database
Offers a number of species and photos, most of which are licensed by Creative Commons.
Bugguide.net
Large number of insect images. Click on name of contributer for licensing information and follow the directions (i.e. some may require contacting the photographer, others may allow free usage)
Bugwood.org Image Archives
A joint effort of many universities and other organizations. Information about image usage can be found here.
Creative Commons
This site offers a variety of "licenses" for images, inculding free educational and non-commercial use. Read here for a good intro about photo usage on Creative Commons.
Iowa State Index of Internet Resources: Image Galleries
Variety of sites collected by Iowa State that have insect related photos.
Google Images
Search for your topic, then choose "Images" from the top menu. Once the images come up, click on "Search Tools," then "Usage Rights." Check any of the "Labeled for reuse" options, as this will limit your search to images that allow free image usage for non-commercial and educational use.
From Mississippi State University, this site allows you to search for photos of moth species. Contact individual photographers for image permission.
Offers free images and royalty free stock; searchable site.