Hi, thanks for your feedback, appreciated. :)

According to this wiki page https://wiki.openstreetmap.org/wiki/Multiple_values
suffixes are fine. Unfortunately, we can't use semicolons, first because it would hit 255 chars limit, and second, because we need to accompany each image with `:path` tag - see https://wiki.openstreetmap.org/wiki/Key:wikimedia_commons:path 

The MV rules document several suffixes, and let the user decide. I searched through taginfo and found just "*1" more common than "*_1". But I am open to use any of those two. 

I don't particulary favor "*:1", becuase colons are often use for subtags - which this is not.