What are some of the earliest graphics (drawings/carvings/etc.) clearly attempting to depict some concept of the infinite (infinite divisibility or embeddings, infinite extension, infinite number)?
What are some of the earliest depictions of a line or curve extending to infinity in one direction? opposing directions?
The earliest depictions - don't ignore the plural form.
So far, the earliest examples are related naturally to temporal extension and religion, not surprisingly, given the diurnal, lunar, and seasonal cycles and the cycle in nature of birth and death.
Theoretical arguments concerning infinite geometric divisibility and extension are associated with the Greeks some 2,500 years ago.
The earliest mirrors were made at least 6,000 years ago, I expect some of the prosperous with exceptional mirrors at some time played with multiple reflections, which continue to amuse movie audiences today, made the mental leap to an infinite number, and felt compelled to record their observations and idea for others in schematics/drawings that may have survived somewhere, particularly since religious significance was often associated with people's reflections in mirrors. (I'd be interested in a verbal record of this as well.)
Look at the highly suggestive recursion of triangles in two columns of these 5,000-year-old [temple mosaics] of Uruk in ancient Sumeria.