As long as you do not pass off the work (music) as your own you should be okay. You don't say what the pictures are of but I am guessing they are family pictures with a popular song as the theme. Add the song title, artist, and composer and maybe the distrubitor (Columbia Music for example) to the end of the slide show. You are probably not planning to make any money on the slideshow but if you do you need to contact ASCAP and BMI and ask about royalities.
The three companies that will go after you the fastest for copyright infringment are Disney-The NFL-Harley-Davidson. If they think you have violated their copyright they will send a cease and desist letter, if you do not comply they will go to court.
To anyone who owns a business: You can not play CDs, DVDs, a radio, TV in a business unless you are paying royalties. If you look on CDs DVDs ect you will see somewhere on the item itself or the packaging "For Home Use Only" or some similar warning. This is why cable, satellight TV and radio is more expensive for a business these companies pay the royalties for you.
I have some musician friends one of them has 14 gold records. I have learned a lot from them. I am not an attorney and I am not giving legal advice, just a little wisdom I picked up over time.