I recently discovered that in Pencil I can add all sorts of other stuff for wireframes. Below is a Material Design template that I recently used to create some wireframes I needed.
Adding Collections avails more wireframes that one can use. These are easy to drag and drop into your canvas and generate some awesome wireframes.
This might not be as "perfect" as paid tools, but it does give a punch to get one going.
I used, and enjoyed, Pencil quite a bit for a while until I got tired by the bugs. Then I found WireframeSketcher, which I've used ever since. It's not free, but it gets updates, it's really good and has a very response developer. Read more at https://wireframesketcher.com/
It's been at least three years since I used Pencil so it's quite possible they solved many of the bugs that I faced.
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