
Avoron |
Iomedae's sacred animal is the lion, so you could use a cat familiar with the mauler archetype. If a friendly caster ever feels in the mood to polymorph your cat into an actually lion, so much the better. It won't be great at combat, but it could be very thematic and could help set up Solo Tactics use.
If you ever feel like getting an Improved Familiar, a Harbinger Archon would probably be most characteristic of Iomedae. Perhaps with the valet archetype for even more effective teamwork feat use or the emissary archetype for flavor (glory domain would give a spectacular bonus to charisma based skill checks once per day, and any planar binding-focused casters would love you).

Avoron |
The companion would have an extremely low HD compared to the rest of the party even with Boon Companion, and would die very quickly. Consider taking the feats Nature Soul, Animal Ally, and Boon Companion for a medium sized lion companion that scales with your level. If you want it to be larger, consider taking a dip in the Mammoth Rider prestige class.