Use a file explorer (I use root explorer personally)
Navigate to the folder that has the pictures you want hidden
Open that folder
Create a new file. In root explorer you push menu, then select new file
Name the file ".nomedia"
You may need to reboot after that. If that still doesn't work, make a new folder named whatever you want, create the .nomedia file in it, move your pictures to the new folder, then delete the old one
"Is life so dear, or peace so sweet, as to be purchased at the price of chains and slavery? Forbid it, Almighty God! I know not what course others may take; but as for me, give me liberty or give me death!"
-Patrick Henry, March 23, 1775