Is there any legal action I can take against Fuji Film Processing for losing my photos?

Yes--there may be a contract provision that states that they are "not liable for negligence, ect" however, many of these "adhesion contract" provisions have been found to be unenforceable. I would take them to small claims court and sue them for the value of the photos and for non-economic damages up to the maximum amount of the jurisdictional limit under a breach of contract theory AND a conversion theory, as well as a negligence theory. I am not licenced in your jurisdiction so this is meant to be advice under general tort law principals, but I beleive that you have a clear case. Also, the correct defendants would be Walmart as well as Fuji. Walmart was clearly acting as an agent in this matter and cannot "pass the buck".