On my RX 560, with kernel 4.18.10, Debian/testing, clinfo says "Image support: no".
I've read about those hacks using LD_LIBRARYP_PATH to pick up the libraries from AMDGPU-PRO driver, but this does not seem to work.
What is blocking OpenCL image support for Linux?
(I intend to do some graphics processing with GEGL.)