Oil Lamp with Sheep and Staurogram
Archeological Museum, Split, Croatia
The staurogram represents the crucified Christ, as explained on this page. The approach of sheep representing the faithful to a symbol of Christ is common in paleo-Christian art.
The label in the museum speaks of two sheep in the image, but I can see only one.
This image in full resolution
More of the sheep/lamb symbol.
More of the staurogram symbol
Source: Photographed at the site by Richard Stracke, shared under Attribution-NonCommercial-ShareAlike license.