No, there shouldn’t be a size limit (other than memory). 10^8 elements work for me:
julia> @time PyCall.array2py(rand(10^8));
34.658970 seconds (100.00 M allocations: 2.235 GiB, 26.95% gc time)
(I double-checked, and PyCall calls PyList_New and PyList_SetItem, which take 64-bit integers … assuming you are using 64-bit Julia and Python.)