According to the Debian Menu System manual, section 3.7, menu icons
should be in xpm format:

https://www.debian.org/doc/packaging-manuals/menu.html/ch3.html#s3.7

Version 02.17-1 switched to an svg. Lintian has a test for this, but
it is masked because the menu file that gets installed still points to
a (non-existant) xpm file (#767046). When the path is corrected,
lintian will emit the following error:

E: lshw-gtk: menu-icon-not-in-xpm-format usr/share/pixmaps/lshw-gtk.svg
N:
N:    Icons in the Debian menu system should be in XPM format.
N:
N:    While other image types (e.g. png images) appears to "just work", window
N:    managers are not "required to support them". Accordingly using non-XPM
N:    icons could break interoperability.
N:
N:    Refer to Debian Menu System section 3.7 (The icon field) and
N:    http://bugs.debian.org/591812 for details.
N:
N:    Severity: important, Certainty: certain
N:
N:    Check: menu-format, Type: binary
N: