uFlow is a Sketch symbol library that I've created to quickly create flowcharts, and IA diagrams.
Flowcharts
13 different connectors 12 gesture indicators Notes 3 cap styles 3 different line styles Templates
uFlow comes with to Templates to help you create IA diagrams and Wireframe flows.
I've always collected design resources, but to be honest I tend to not look at my collection first when looking for something specific.
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Unsplash.com is always my first stop for photos, and I always "purchase" the free goods of the week on creativemarket.com because it saves them as purchases for future use (still only a single use license though).