Use icons

README.md

@@ -23,10 +23,20 @@ As part of the RIOT project, the [RIOT code of conduct] applies.
 Projects using RIOT OS
 ----------------------
 
-* [Marian's Business Card](https://github.com/maribu/business-card): Hardware description, board support, games and text display software for business card sized board with USB power supply.
-* [Marian's demo boards](https://github.com/maribu/boards): Various PCBs, including an RGB Christmas tree board, along with RIOT board support for most boards.
+Icons indicate that the project offers
+hardware descriptions (![oshw]),
+a RIOT board description (![board])
+or RIOT applications (![app]).
+<!-- Right now we have nothing on the list that is modules only, could get https://game-icons.net/1x1/lorc/jigsaw-piece.html as an icon then -->
+
+* ![oshw] ![board] ![app] [Marian's Business Card](https://github.com/maribu/business-card): Hardware description, board support, games and text display software for business card sized board with USB power supply.
+* ![oshw] ![board] [Marian's demo boards](https://github.com/maribu/boards): Various PCBs, including an RGB Christmas tree board, along with RIOT board support for most boards.
 
 More lists
 ----------
 
 * [Hackster](https://www.hackster.io/riot-os) has an own list of projects using RIOT
+
+[oshw]: .icons/oshw.svg "PCB available as Open Hardware"
+[board]: .icons/board.png "RIOT OS board definition available"
+[app]: .icons/app.png "Application available"