Iconography is an import part of UI design. Icons should make it easy for the player to know what a button will do. It's always a good idea to use an icon instead of, or along side a button label to allow the player to understand it's function without having to read. Icons can also make it easy for the player to find information on a dense screen. For examples of what Insurt looked before icons were added, take a look at this post.
All of Insurt's icons were created either by myself or BitBlox. Here he has explained his process in designing the icons for Insurt.
An icon for Insurt being created in Blender
"When comparing Icons to things like characters and scenes they can be pretty simple. However they too usually go through there own, sometimes lengthy process of development into a final result.
In blender you would first model a shape for the icon and render it out with a transparent background. Afterwards going though iterations of changes to eventually get a nice result. As with most things I would recommend looking at reference and receiving feedback.
When I was working on these icons using blender, some stuff worked fairly well. Like vertices to make complicated shapes quickly. In general though, I would not use blender for creating icons in the future. For the speed of a production, making accurate changes to 2 dimensional shapes can be difficult and overall the methods of creating images involves rendering using emission materials. I would instead definitely recommend learning Inkscape, which is a amazing vector graphics tool. However that said blender is still one of the best '3D' programs out there, and was used to create some of the 3d models in Insurt."