This might be a very bad idea in some ways ...
Let's say that you have a client with a bad drive. You recover the data by PC-3000 / DE / Head Swap, whatever. You charge the client for exampl $1000 USD.
Now the client checks the data and he figures out that he have 1000 images that are very important to him/her that are damaged. This might happen because media/platter damage that you didn't notice.
Now what will you do ? Recover/restore the 1000 images by hand because the client already paid ? Or you offer the image restoration service at $10 for each image ? Wouldn't the client fell that it's sort of a scam ? Like having an initial payment and then another payment to recover the lost images ?
Unless you clear state when doing "normal" data recovery cases that in case of damaged images the price have to be paid acording to the images the client wants to recover ?
On that thought, my paperwork that my customers sign explains about bad sectors and that the service doesn't include any file repair or restoration services. However if I plan on pushing such service onto customers, I'm sure I'll need to make it even more clear up front. Perhaps I'll even offer a few as part of the recovery cost, but if they want more it'll be extra. As it is now we'll do the occasional PST repair and whatnot, just to make the customer happy and avoid them returning asking for that help.