There are three ways to do this. The SD card in the 3DS is identical to SD cards that are used in digital cameras. All you have to do is take the SD card out of the 3DS, put it in your computer (if you have an SD card slot or SD card reader), and find the pictures and copy them. I just opened up mine to find where the pictures are for you. If you plug in your SD card to the computer and open it, there are 2 folders: 3DS and DCIM. Go to DCIM --> 100NIN03, and your pictures should all be right there to copy.
If you choose to do it this way, I have one warning for you - DO NOT, under ANY circumstances, move anything or delete anything in the "3DS" folder. You don't want to corrupt your game. I don't know what happens if you delete the pictures off of your card, but I doubt it hurts anything.
The second way to get the pictures is to get on the 3ds GlobalLink. Your latest picture will be there, and actually they all might be there. I'm not sure.
The third way is to set up a Dropbox account. Dropbox's "basic upload" feature is compatible with the 3DS browser, and you can upload your pictures to your computer straight from your 3DS.
Thank you Varanus!
I thought they were stuck in my DS forever (kind of short sighted on part.)
Thank you for figuring out how to do it.
I know I'm not the one who originally asked the question.
I wish reputations were back you earned one for this.