wouldn't it be quite hard to observe these furry critters? NGC 4676 has an apparent magnitude of 14.7 and an angular size of 1.4 arcminutes.
The picture in the link vindictive posted, taken by hubble, is explained in more detail here
My guess is that it would probably look like a faint smudge in large scopes. I have not observed it myself either. Maybe someone else has seen these mice or have tried to find it that can confirm or dispute this. Happy hunting!