It's probably been there all along but I only recently noticed the "My Pictures" folder listed for media in the playlist view of VLC. "Ctrl + L" toggles the playlist view on or off. Or go into "View" (top menu) and click on the first option "Playlist". I clicked on "My Pictures" on the left-hand menu and saw my pictures and other folders. I double-clicked on a picture and it opened for 10 seconds then it went to another and then another and so on. This is how I discovered you can watch a picture slide show through VLC.
Then I wanted to know was if I could adjust the time each picture displays before going on to the next.
Click on Tools -> Preferences or "Ctrl + P"
Click on the word "All" down in the lower left-hand of the screen next to the "Reset Preferences" button.
Then in the left-hand list of settings find "Input / Codecs" Then "Demuxers" – click on the little arrow before each selection to expand the options if necessary. Then click on "Image".
Now on the right-hand panel look for "Duration in seconds". It is 10 seconds by default. I changed it to 5. Use the arrows to adjust or just type it in.
Then click on "Save". No restart necessary but if it doesn't take effect right away then restart.
Adding/Removing Pictures
Option #1
Just add the pictures to your "My Pictures" folder. The downside here is that once VLC gets through that folder it automatically goes to the next folder if any. It will keep running till it can't find any other pictures. Also you cannot delete a picture from the playlist. I could not find are way to refresh the list without restarting VLC.
Option # 2
For a more customized slideshow you can create a playlist. Go to the playlist view (top menu View -> Playlist or Ctrl + L) of VLC and just drag and drop the pictures you want to appear on your slideshow. Double-clcik on the first picture listed and let the show begin.
Option #3
Open VLC -> Open Miltiple Files (note:open folder option doesn't work) -> Click on the Add button
In the box that opens, towards the bottom right-hand corner click on Media Files box and click on "All Files (*)" in the menu.
Now you'll be able to see your pictures. Select the ones you want (hint: hold down on Ctrl while selecting files to choose more than one at a time or Ctrl+A to select all). Then click on Open. You'll see your files listed in the File selection box. Now click on Play.
Add Music
You can play a music file over the slideshow but it doesn't work very well in my case. The music restarts with every new slide. But if you want to try it for yourself.
In the Open Media box click on "Show more options". Then check "Play another media synchronously (extra audio file,...)".
Click on the Browse... button. In the box that opens click on Add.
As before, in the box that opens, towards the bottom right-hand corner click on Media Files box and click on "All Files (*)" in the menu. Find your audio file on your system. Clixk Open. Now you should see the music file added to the selection box (in my example, BoB Porter). Click on Select
Now you'll be taken back to the previous screen. Click on Play.