Celtic pottery which was used every day was usually rather dull and plain. It was for function rather than anything else. Sometimes you would get a bit more of an ornamental piece:
Sometimes a simple pattern etc. would be added but as most Celtic pots and ceramics go, they stayed rather plain. If a Cruet set was going to be made with god’s and offerings/rituals in mind, it would be more elaborate. Items such as the Battersea shield were labored over and made so elaborately to be thrown immediately into the rivers as offerings. A temporary shield wouldn’t be so elaborate. Just in the same way a ‘ritualistic’ cruet set wouldn’t be so plain.