For item types, part types and issues, Architects typically select icons to be displayed in the swExplorer client so that users can easily distinguish between different types. Architect users can view all icons available for items using the swArchitect client. 

Select any item in the Type structure tree and click on the look-up button for Icon

There are also a couple of methods to retrieve the icons via the API: 

// Get an array of bitmaps containing the standard SystemWeaver icons.

> Returns the SystemWeaver icons as bitmaps.

// Get an array of image sources containing the standard SystemWeaver icons.

> Returns the SystemWeaver icons as image sources.

//Prior to release Kålltorp R46, the methods were  SystemWeaver.Resources.SWImages.Instance.MetaDataImages and
SystemWeaver.Resources.SWImages.Instance.MetaDataImageSources respectively. 
Also, with the earlier releases, it is not possible to retrieve icons using the Nuget package. To do this, you would need to use the SystemWeaverClientApi.dll.