Ah, I see now. I downloaded and set up a Spanish pack but it looks like the pack has to exactly match the UBB version. The one I tried had lots of missing icons and links as we have UBB 18.104.22.168.
Do you know anywhere that might have that available?
Well I searched for spanish packs here and I see two of them.
Since they are dated a few years ago.
Then yes if a language string was added over the years then that string would not be populated so some may need to be edited in the control panel
As far as missing icons I don't recall any images used in a language string.
But anyway can you provide the url where you have it installed and what pack you used.