Once again, the QlikView Developer Toolkit (available on Qlik Community) can be a good starting point to assemble an image collection for your dashboards. However, chances are that after a few weeks you will need more specific icons, symbols, and buttons to enhance your applications. If that is the case, there are several websites such as http://dryicons.com/ and https://www.iconfinder.com/ where you can download amazing packs with a freeware license.