It could be useful to have firewall groups for ICMP Types. Particularly for IPv6 where you often need multiple types.

Proposed syntax:

set firewall group icmp-group type <name of ICMP type>
set firewall group icmpv6-group type <name of ICMPv6 type>

set firewall ipv4 input filter rule 10 icmp group <name of icmp-group>
set firewall ipv6 input filter rule 10 icmpv6 group <name of icmpv6-group>

It could allow for concatenation of the element so you can have the type/code pair, but I think that might make things messier and harder for user's to understand. If an explicit type/code pair wish to be matched, that would remain within a single firewall rule.