Hi there!
I've got a shell tattoo after my first Camino too. Couple of thoughts (assuming that you are new to the world of tattoos):
- even though the tattoos will probably be small you want them to be *good* - so research the specific artists is a must. That might be more easy to do for people located close to you (reading reviews in Spanish might be tricky)
- your bodies / skin might be pretty messed up during / right after the walk. This is problematic for several reasons: a) you are more prone to feel pain if your body is already stressed and b) damaged (sunburned) or bloated (salt levels) skin wont retain ink well
- think about the location. Say you want the shell on your feet - how are you going to walk in hiking boots afterwards? If you have them on your arms, how are you protecting them from the sun. Plus potentially questionable hygene in the albergues. If you *need* to get them in Spain (I get that completely) do it after the walk and at least *two or three* days rest in Santiago. There are a few threads about Santiago-based tattoo artists here - I'd also suggest checking out their online presence to see the actual work.