There are a lot of open source projects make developers job much easier. I always prefer lightweight plugins. Lightweight means they are not the most comprehensive and robust ones. But they are easier to be customised to meet all my needs.
If you are looking for image slider jQuery plugins, you definitely need to try slick. It is easy to start with and allows you to style it in any way you want. It also supports responsive design.
If you want to have custom styled datetime picker for your website and you don't like include many other redundant jQuery UI in your site, jQuery DateTimePicker is the one for you.
Again, if jQuery UI is not your favorite, then try jQuery Sortable.
There are quite a few options, Dropzone is my personal favorite. It supports single or multiple file uploads. It also supports drag and drop file uploads. You can easily configure backend to process uploaded files. That's all you need, isn't it?
Are you trying to make your background image looks fancy without heavily coding? ParallaxJS does all the job for you.
Have questions? Feel free to use the form or send me an email with any questions.
I will be responsive to your requests and your questions.