You might not want to repeat Fenrir, but an image of Vidar slaying Fenrir on your right forearm, or worked into the left somehow, could match the Thor/Jörmungandr scene pretty well.

https://www.ecosia.org/images?q=fenrir%20and%20vidar

You might want to thinking of doing Yggdrasil/Hoddmímis holt as the place Líf and Lífþrasir go to survive Ragnarok. They are the two humans that survive Ragnarok.

Someone mentioned Freyr and Surtr fighting. I've always liked this image of Surtr

https://en.wikipedia.org/wiki/File%3A_The_giant_with_the_flaming_sword_by_Dollman.jpg

Also most likely the three Norns survive Ragnarok and certainly play a role in the myths. Also think about the death and ressurection of Baldr.