The images on this page are from Font-de-Gaume and they are scans of postcards. Flash photography is not permitted at either Lascaux II or Font-de-Gaume, and trying to take a picture in those caves without flash is a waste of time. The two sites are very similar with this exception: Lascaux II is a copy of the real cave and is located a few hundred meters from the actual site; Font-de-Gaume is the real thing. Of the two, Font-de-Gaume is the most impressive. Whether this is because it's genuine (rather than a model) I can't tell. I only know that it took my breath away.
Both Lascaux and Font-de-Gaume are Magdalenian sites. That is, the recent paintings date from about 14,000 years ago. Lascaux is older -- around 17,000 years ago. The Cro-magnons who painted these pictures are our immediate ancestors. They didn't live in the caves, but probably used them for councils or rituals. The animals painted were of the sort found in the local area.
If you go... It's incredibly difficult to get reservations at Font-de-Gaume (and they're necessary). Their phone is answered in French only, so if you're not fluent in French, tough luck. They do have a fax and that's the absolute-best way to get in touch with them since it gives them time to get the words translated. Lascaux is easier; they're much more commercialized, and that's the bad news.
Our tour of Lascaux II included more than 40 people and it was crowded. If that's how they did tours before closing the caves in 1963, it's no wonder the paintings deteriorated.
The tour of Font-de-Gaume was 12 people. No carryables of any sort are allowed in the cave. No purses, handbags, backpacks, or camera bags -- nothing. Some parts of the cave are quite narrow and visitors find themselves crabbing sideways with their hands upraised in order to avoid brushing past the walls.