Hi April
This would be more of a module function rather than a template function. There is some modules included with our templates which may be suitable. You can also check out the Joomla JED (
http://extensions.joomla.org/extensions/photos-a-images/images) where some alternative options should be available.
If you are fairly confident in CSS and HTML you can also try creating your own using a Custom HTML module or just adding the code directly to your articles. CSS can be added to the Custom CSS field of your templates parameters.
CiarĂ¡n