I understand why you might have doubts about "attributes": because in general English likes to use the word for abstract qualities or characteristics. In fact, though, it is a term accepted by (say) art historians for this very context.

To demonstrate the point, I recommend the following googles:
"attribute of St."
"emblem of St."

You will see that the English-language literature supports both. (Ignore of course anything translated from another language or seeming to have been written by a non-native speaker)