First let me say welcome to the CiC forums from me.
Second that this isn't a bad photo.
You asked how it could be impoved, not knowing you level of experience, I may mention stuff you already know, but I am trying to 'cover all bases'.
It is quite noisy, now I know (from the EXIF data) it was shot at ISO 1250, but that alone (on a Nikon D90 DSLR) shouldn't result in this much noise unless;
a) it was a significant crop from a larger image
b) shot in jpg with a fairly high in camera sharpening applied
c) it was under exposed and you had to raise it in PP (post processing)
d) more than one of the above
It looks to have focused on the whiskers, not the eyes - with anything that has eyes, it is always better to focus on them
Your aperture at f/4.5 didn't give much Depth of Field (DoF), which hasn't helped the slight mis-focus
Miss Kitty is back lit, so her eyes are in shadow, so we can't see as much detail as might be desired - perhaps a sheet of paper as a white reflector would help with that and also give us a 'catchlight' effect (reflection) in her eyes.
There's just a hint of something in the lower right corner, it could have been cloned out or cropped off ideally
I could say "move her to a brighter place", but then we wouldn't see the 'large eyes' (open irises) we do, which are nice
Your shutter speed, at 1/30s, risks blurriness due to camera shake or subject movement, but that said, I don't see any
Other things that are good:
Non distracting background (soft, good colour, etc.)
Hope that helps,