HOW MANY PICTURES CAN I HAVE ON MY FLAT FEE MLS LISTING?
Depends on your FSBO package you purchased as to how many pictures are included - however you can always add more by adding the "Showcase" enhanced upgrade.
The max number of pictures you are allowed varies per the MLS system:


BRIGHT (Northern VA - Fredericksburg Area) is 50 pictures
CAAR (Charlottesville Area) is 75 pictures.
CVR MLS (Richmond Area) is 50 pictures.
CBRAR MLS (Chesapeake Bay Rivers Association) is 46 pictures.
REIN (VA Beach/Hampton Rds Area) is 50 pictures
WAAR  (Williamsburg Area) is 50 pictures
EASTERN SHORE MLS (Accomac and Northampton) is 36 pictures
HRAR (Harrisonburg and Rockingham Area) is 75 pictures.
LAR Lynchburg is 99 pictures.
NRV MLS (New River Valley Area) is 125 pictures.
RV MLS (Roanoke Valley) is No Limit.
SWVAR (Montgomery and Surrounding Areas) is 50 pictures


Slideshow pictures are critical to buyers - they want to see if they like the home before they sit in traffic to see your home.
If you don't have pictures of certain rooms - the buyer wonders what is wrong with that room that you are not showing it.