It'd be good if rsvg-view was included in /etc/mailcap as an svg
handler.  This allows say

    see /usr/share/reportbug/debian-swirl.svg
    =>
    runs rsvg-view

I get some joy from librsvg2-bin.mime below installed to
/usr/lib/mime/packages/librsvg2-bin.  If you chuck it in as
debian/librsvg2-bin.mime the debhelper dh_installmime should install it
there automatically.

The "priority" is a matter of cooperation among viewing programs to
establish a sensible order.  Does rsvg-view do more than I saw?  Feel
free to raise its priority.  Presently there is no mailcap svg at all
among what I have installed so rsvg-view is better than nothing :-).