Usually, I am not a big fan of heraldry being used as a decorative motif on vestments and pontificalia. Every now and again, however, it can work. The example below shows the Most Rev. John J. Myers, Metropolitan Archbishop of Newark, NJ. The chasuble he wears is decorated with a shield (partially obscured by his pallium) bearing his personal coat of arms as is the base of the mitre he is wearing. I think this is a good example of how heraldry can be used to decorate vestments in a way that is neither overpowering nor inappropriate.
EXARANDORUM 
The one unfortunate aspect of the pallium: blocking the designs on a chasuble. This is perhaps one of the reasons why Benedict XVI originally chose to wear an older style of pallium since it did not block the design on vestments.