Rule #1. Have a receipt. If you have a receipt, you begin in a decent bargaining position, because you have proof that at some point in time someone paid for a piece of merchandise. It might not be you, it might not be within 90 days, and there might be some irregularities, but in general, having a receipt is like starting a poker hand with a pair of aces.
Rule #2. Don't try to return photos you made using the Kodak PictureMaker machine. You scanned them. You cropped them. You made them look like something a blind baboon flinging poo on a wall could duplicate. Stupidity is not an excuse for a return. If it were, your parents would most likely be childless.
Rule #3. Don't try to return the aforementioned Kodak PictureMaker atrocities months after you allegedly paid for them. That's like buying a chicken, roasting it for Sunday dinner with some potatoes, carrots and a nice stuffing, then using the bones to make chicken soup - then trying to return the bones after the dog gnawed on it in the yard for a week. You've had those awful pictures for months. If you were truly "horrified" at them, you would have never paid for them.
Rule #4. Don't blame the entire incident on a nebulous "aunt" who picked up the pictures. Ray Charles and Stevie Wonder wouldn't have paid for those. Much less the $19 allegedly paid for those pictures.
Rule #5. No, I don't feel sorry for you that you needed to "send them off for a scholarship" and you "lost the pictures" until now and you had to "send off the originals." For 19 bucks you could go to a PhotoBooth at the mall if you need quick snaps. Or even the Wal-Mart Portrait Studio. Or get a friend with a digital camera. You get what you put into it. Consider it your first post-high-school lesson. Since obviously cause & effect never sunk in.
Rule #6. Pointing to the barcode on the envelope the photos came in and saying "This is the receipt, right here," is really not going to work. Are you sure this was for a scholarship and not for a parole application?
Rule #7. I know EXACTLY what you did. You needed an photo for something - and decided to scan in your tiny 2x3 photos from either your prom or graduation - and blow them up to 5x7 or 8x10 size. Really, you should know better. If you don't, ask. Bigger is not always better. You'll learn that one in college too!
Rule #8. You don't have a receipt, you don't even have anything that can be tracked to show your original order. Those envelopes come with every order. Who's to say you didn't order double prints of your vacation photos and use that envelope?
You also don't have anything that offers a shred of proof you ordered the pictures from this Wal-Mart. You are the one who produced that work. You had the chance to look at it before you paid for it. Please tell me - what does Wal-Mart owe you? Besides a good hard smack upside the head?