So I was having yet another try at getting to grips with basic Cycles-- Emission, Reflection, map/masking each, trying to get both FX to work at same time...

No, Cycles Surface would only accept one of Emission nodule +Image_Map or Reflect nodule +Image_Map....

D'uh, what was I missing ??

Much exasperation, caffeine and unprintable epithets later, sorta dawned that perhaps the 'Blender' thing meant 'Combiner', rather than a 'me-too' of an arcane Blender / BfA (Modeller) specific feature...

{Face-palm...}

Upside, I've learned something new today...

A tad fuzzy due 14 pixel-sample test render...

ps: May we have more than 10-character fields for image_source name, to better distinguish related files ??

What exactly are you trying to do?  You can't have illumination and reflection on the same object at the same time.  It's physically impossible, IMHO.  If you own P12, you can use the PrincipledBsdf instead of separate nodes.  However, an actual Cycle Reflect node does not exist in Poser, instead, you should use a Glossy Node for reflective surfaces.

Actually, I take it back, you can have emission and reflection at the same time.  But you need to set your emission strength very low; in the case of the images below, the emission node is set at its default value of 1.  Any higher and the illumination will overwhelm any reflection associated with the cube.

My crude 'proof of principle' has different masks for reflection and emission of the box's single material, but the 10-character field only shows common part of names.

FWIW, there's something weird going on, as only a circle should reflect, not whole face. I'll try to figure it when my kaleidoscopic migraine subsides.....

When using the blender node with a mask, you want to set the blending to 1 and then plug the mask image into that. A blending value of 0 uses the top input only. A blending value of 1 looks at the bottom. Setting it to .5 will mix both. When you plug in a mask node, the white is equal to the value set and the black is 0.

Try:

You can also try using cycles nodes. The glossybsdf node might give you a sharper reflection than the reflect node.

I switched to the mixclosure node to show you how you would set that up if you want to try that. You can use continue using the blender node instead. It will work the same with the cycles nodes.

Oh, I forgot to mention, since you can't see very many characters in the image name, you can change the name on the node itself to help you keep track of which node is for what