Last night, I have encountered an issue concerning Sitecore Icons which went missing. I have installed a fresh Sitecore Instance and when opening the CMS, most of my icons were not loaded. Even after restarting IIS, the issue was not solved. During this small post, I will explain how I have resolve this problem.
If you have a current Sitecore Instance running with all the icons loading properly, go to the Website folder. Search for the folder temp. The temp folder contains all the different icons that are being used in the Sitecore CMS. If I am not mistaken, the files present in the temp folder are files that have been cached.
You can copy the temp folder and paste it in the new Sitecore Instance website folder. You need to overwrite the files if the overwrite popup appears. After the copying process is completed, open your Sitecore Back Office and see if all your icons are now present.
If you do not have any other Sitecore Instance, let say you are installing a new instance on a formatted PC / Laptop, you may ask your colleagues to provide you a copy of the temp folder.