What seven french nouns ending in age are feminine?

Assurance-chômage, cage, image, nage, page, plage, rageare the only ones.

The suffic "age" matches mostly masculine nouns because it means "the act of", followed by the noun or verb it refers to. This construction would normally be neutral, but since there is no neutral gender in French, masculine is used instead.

The only exceptions are Words that end "naturally" with "age", but not as "the act of" suffix, just from normal spelling. These nouns are usually short because they are not extensions to existing Words, and even then, probably half of them are masculine, such as "âge", "étage", "gage", "sage".

The other exception in my list is the compound Word, which takes its gender from the first Word, but the second Word in "age" would be masculine on its own.

There are some dedicated tools on the web that can return processed lists of such Words. Search for instance for "mots qui se terminent par age".