I’m guessing many Tulip users have had to search the internet for icons outside of the standard library within Tulip, and I’m guessing many users also have access to PowerPoint. Well, PowerPoint is actually a great place to search for all kinds of icons and you can copy and paste right from PowerPoint into the Tulip app editor, while preserving the transparency of your icons!
Once you’ve inserted your selected icons, you can create assemblies of icons, like this circle + trashcan I created:
Then you can actually just highlight all the desired icons, Ctrl + C, then go to the Tulip app editor, and Ctrl + V and it will paste right in there as a single image, but with your colors and transparency preserved!
PowerPoint icon library is large, and if you have an online version also connects you to an even larger online library of icons.
https://thenounproject.com/ is another option, and includes massive amounts of industrial themed icons. Pricing and terms vary by creator; many are free with attribution.