Next time you want to delete a mystery thing, first copy it to a backup folder. Only delete the backup copy after you are sure it had no ill effects to delete them from the original place.
Have you looked in the recycle bin?
When you delete a file, it only removes the reference to it in the file table at the start of the disk and declares that area to be free and available to save other files onto, it doesn't actually wipe the area where the files themselves are stored yet. So you might be able to Undelete them if you're quick.
You could try one of the many programs which undelete accidentally deleted files, such as Gary Undelete. Trouble is, every time you save a file onto the same drive where you deleted these files, you could be overwriting the area which contained them. After their data area has been overwritten they are gone forever and no file retrieval software can get them back. That includes installing a new undelete program onto that drive, so if you have another partition or hard disk available, download and install the undelete program there instead of onto the drive containing the deleted files
Maybe this "recently changed" folder only held a copy of those files. Have you tried searching the whole hard disk for the filenames of those pictures?