A surfeit of textures ? Uh-huh. Either your render comes out in shades of grey, or your prior renders vanish from side-bar, or Poser simply 'falls over' as the 'garbage collector' crashes...

At least if you're converting 4k PNGs or TGAs to JPGs with ~1/10 file size, you're also set to down-size pixels to 2k, 1k, ½k for lesser levels of detail...

I'm most familiar with {free} Irfan View for graphics wrangling. Digging around in the batch tools, I've just found additional down-sizing options to match the single tools. But, without scripting tools to auto-pour each down-size into appropriate sub-folder, only one ratio at a time. You'd need to be so wary of what went where...

-- I port a lot of freebies from eg XPS via FBX, or MMD's PMD/PMX via OBJ/MTL. Remembering to mirror latter's meshes left/right before export, of course, of course. Too many come with a vast zoo of huge PNGs or TGAs. And then there's the misery of having to extract the 'Alpha channel' from each 'diffuse' or 'metallic' to use as Poser's transparency map....