Apart from the official campaign shields a number of unofficial or prototype campaign shields also existed.

Balkan Shield (Balkanschild)

This shield was to be presented to the German forces fighting against the Red Army and the partisans in the Balkan 1944 and 1945. It was designed by Benno von Arent and had the text "Balkan" with the dates "1944" and "1945" on either side of an eagle with swastika over a map of the Balkans.

Dunkirk Shield (Dünkirchenschild)

The Kriegsmarine base at Dunkirk was surrounded by the Allied forces after their landings in 1944 but the Kriegsmarine soldiers and unit from 226. Infanterie-Division fought on until the end of the war under the Konteradmiral Frederich Frisius.
The shield was crudely made with the text "Dünkirchen" and the numbers "19" and "44" on either side of the watchtower in Dunkirk.

Lorrient Shield (Lorientschild)

The Kriegsmarine base at Lorrient was the home of 2. Unterseebootsflottille, 10. Unterseebootsflottille and 14. Unterseebootsjagdflottille and was surrounded by the Allied forces after their landings in 1944 but fought on until the end of the war under the command of General der Artillerie Wilhelm Fahrmbacher. A crudely made campaign shield was produced starting late in 1944 with the text "1944" and "Lorient" with a nude warrior carrying a sword and shield standing on a U-boat pen based on a design by Marinebaurat Fehernberg.

Memel Shield (Memelschild)

During the winter of 1944-45 Memel (Klaipėda) was under siege by the Soviet Red Army and an unofficial campaign shield was instituted, most likely by Generalleutnant Dr. Karl Mauss who was the commander of 7. Panzer-Division.
The shield displays the arms of Memel, three towers, with "Memel" written above and "Njemenfront" below. Only a few examples were produced, it is not known if any were issued.

Stalingrad Shield (Stalingradschild)

This shield was supposed to honor the men of 6. Armee fighting in Stalingrad in the fall of 1942. The first prototype was designed by Ernst Eigener (who served in Propagandakompanie 637 in Stalingrad) and featured a closed wing eagle on top of the shield with the text "Stalingrad" below. The three silos that were important landmarks in Stalingrad were pictured below the text with a dead German soldier with a crown of barbed wire in front. This design was rejected and a second one with a river with the text "Wolga" instead of the dead soldier was submitted, this time by Generalfeldmarschall Friedrich Paulus, Eigener had been killed in the fighting. The shield was never made official due to the surrender of the Axis forces in Stalingrad.

Sources used

Christopher Ailsby - World War 2 German Medals and Political Awards
John R. Angolia - For Führer and Fatherland: Military awards of the Third Reich
David Littlejohn & C.M. Dodkins - Orders, Decorations and Badges of the Third Reich
Robin Lumsden - A Collector’s Guide to Third Reich Militaria
Richard Mundschenk - The Lorient Shield: An unsolved mystery (in The Military Advisor, Vol 1 No 4)