Question: Can you run fsck on a disk image or raw file?
Answer: I believe you are referring to KVM disk image/raw files. It could be the disk image created from a dd clone. The answer yes, you can run fsck on a disk image. You can also use other fsck attribute as required as following:
fsck.ext4 -fyC /somefile.raw
Remember to use specific partition fsck binary, here, we have used ext4 binary for a ext4 file system loaded on the image file. Running badblock program on an image file can be bad. You may use -c (small c) to run badblock check with the fsck:
fsck.ext4 -C -fyc /somefile.raw
This sometimes create undesired results and not advisable.
Question: What other option do I have?
Answer: You can mount the image using loop back device and then run the file system check. This can be done using kpartx as described in this post: How to: Mount raw VM disk images (KVM/Xen/VMW)