Yep, I got the same thing in response to my WTB ad.
The pic-msg.net site will ask you to install a gimp viewer to view the pictures (initially I thought this was okay because I don't have a smart phone and can't get pic messages), but it's almost certainly a trojan or other virus of some kind. The files at that site aren't even the proper extension. GIMP images are a real thing, but the file extension is .xcf or something, not .gmp
I got the same thing from 6466967719, answer to a "lost" post. Luckily my anti-virus software told me that the downloadable stuff was malicious so I deleted.