I am having a hard time reading these icons even as-is, because the decorative bits (the box with the X and the frame) have the same line quality as the illustrative bits. I can't tell at all what the last one is meant to be. By method of elimination my guess is shield or foot (just one foot?).
The way metal filigree keeps detail like this is by giving certain things different patina, effectively giving certain parts a darker value. Another way it's done is by having more or less detail in some areas, which is another way of creating different values. You could do the same with yours.
Don't be afraid to leave some areas relatively flat for easier readability. You need just enough of the metal look for the thing to look metal, it doesn't all have to be faithfully metallic.
