Your workflow is bit confusing with .7z to .rar convertion?
If it's not .var package just extract images inside
'custom/atom/person/textures/' (in whatever sub-folder inside, example: tattoo or decals)
You can't put zip/rar/7z files inside addonsPackages and hope for it to work, only .var files goes there.
(without proper meta & folder structure it wont load)
So, you have two .jpg images that you wanna use as tattoo on decal slot (torso and limbs)?
Now ideally for decals you wanna use .png (transparent) format, so it doesn't 'overlap' your skin diffuse texture.
But in any case i don't see the reason why they won't show or load at all,
even if using incorrect jpg format or incorrect resolution or incorrect position on limbs/torso parts...
you should be able to load it (unless you have corrupted images)?
Ignoring the resolution, are you sure images are .jpg and not .jp2 (jpeg2000)?
All skin textures should be 4096x4096 res as "optimal", but not mandatory.
Ideally (with not much quality loss):
- .jpg for diffuse, specular, gloss, normals (it can be .png or .tiff)
- .png for decals
Again not mandatory, you can load lower or higher res textures (only 'true' drawback is that auto-gen feature doesn't work with torso textures bellow 4k).
You best option is to get tattoo in .png format first.
If you are using custom textures already than .jpg decal is not gonna work well with it.
In any case
if everything is installed correctly, there's no reason for image to not load/show (it's strange anomaly at best).
You can try clearing VaM cache...