There are several tools that allow you to present images using a computer & digital projector. These tools are particularly useful for classroom presentations.
PowerPoint : Part of Microsoft's Office suite of programs. Add pictures to text presentations, or leave the text out all together!
Keynote : for Mac only. Keynote enables "cinema quality presentations for everyone"
Amazon Prime Photo : Amazon Prime Photos offers free online photo storage to Prime members, who can save and share unlimited photos on desktop, mobile, and tablet.
Photos (for Mac OS only) : Apple's image storage software. Organize and edit digital images, then export to other applications in the iLife suite to share via e-mail, in print, and the web. Also offers a slideshow feature.
Adobe Bridge : part of Adobe's Creative Suite, Bridge indexes documents you produce using the various Adobe products, and provides easy access to Adobe Stock Photos.
Tropy is a new beta tool developed to work with images, particularly archival research photographs. Like Zotero, it's free and was developed at The Roy Rosenzweig Center for History and New Media at George Mason University. Tropy allows you to spend more time working with your research photos, and less time searching for them.