Hi plennert,

the image=* and wikimedia_commons=* tags are used to link images that depict the physical object, not for logos. There's an exception for trekking routes symbols, but even in that case the tag is wiki:symbol=*, not image=* or wikimedia_commons=*.

Some examples with other "emergency" values near here: node/9197283504, way/826170846, node/5526100199

Usually we use operator:wikidata or brand:wikidata in order to link the respective logos (otherwise imagine every one of the 47847 elements mapped as operator=Deutsche Post with 47847 linked Deutsche Post logos). So I god idea in this case could be to create a "Freiwillige Feuerwehr Singen" Wikidata entry and link the logo there and then tagging operator:wikidata=* here.