Scripts without picture are less fun. My advice is to look for pictures galleries, images have often the good size, great quality, and it's not too much difficult to find exactly the good one. Drawbacks : pictures too much hardcore (naked after the 2nd picture...), or not enough natural. Generally it takes 30min to find a full good gallery for a script.
Lets post here the most useful galleries aggregators :
http://badgirlsblog.com/http://www.nngalleries.com/http://www.babefinder.net/http://www.glam0ur.com/http://www.brdteengal.com/http://www.imagefap.com/http://www.hotyoungpussy.org/http://www.thehun.net/http://www.stocking-tease.com/http://www.baberoad.com/Also, most if not all of them work with the gallery import tool of SexScripts (go to the page, copy-paste the address into the import box, wait, add text).
Which size ? As big as possible and the best quality possible, but not too much bytes ! As it is impossible, here is an example setup :
1000px by 800px in JPEG with a 75% quality (that is around 100kb) (so use Photoshop, Gimp etc. if you know how to and you are far from this). Picture will be sized down if needed, but never up.