Free jQuery plugins have given developers access to build complicated systems with little-to-no worries. Pre-built solutions with custom theming offer so much more than free scripts. The plugin system itself was constructed in such a way to provide abstraction for quicker development.
In this article I have put together a brilliant set of free image galleries and carousels. Each one is built on top of the jQuery library and some have alternate dependencies for scripts like Bootstrap. No matter what you need to build, you are bound to find something helpful in this long list of open source plugins.