These humanoid creatures need to walk on four legs. Pretty simple. Their legs also need to be sticky, like a gecko’s, so that they can walk on walls and upside down. They have eight eyes, two normal on the front of their heads, two normal on the back of their heads, two that can see infrared on the front of their heads, and two that can see infrared on the back of their heads. It can also move each pair separately. They are the size of the average human. What other physical effects will this have on them and what changes will have to be made to their anatomy?
Your creature will probably have tiny bristles, arranged in ridges about 5 micometers wide, almost like fingerprints. You'd need to work out the math to estimate the holding power of these things.
You don't need 4 extra eyes to see infrared. All you need are an abundance of rod structures in the retinas of the first four eyes. Of course, it's your world. Rods and cones can co-exist in the same retina.
In order to stick to walls, in a way that is useful for walking, they would need to be light. One way to achieve this would be to have a large, methane-filled bladder somewhere in their body, which would allow them to be floaty enough to stick to walls. This would probably entail a large torso, with skinny limbs as a way to further reduce weight