I don't know what else to call them. I googled for simple icon collections that combine a letter and number like G5, S3, or Z2. Maybe my search results produced nothing because they are listed under a different name, not alphanumeric.
I've tried many times to create my own icons. I have two icon creation apps. Almost any image looks ok when it's big. Icons are usually very small, like toolbar and menu icons. Typically, 16x16 pixels. When I shrink and save my images as an icon they look horrible. Maybe I'm using the wrong apps. If it exists, can you recommend an app that will produce clear icons after the image is reduced to toolbar or menu size?