There are some pretty good 4 foot fluorescent tubes around that are relatively cheap and can produce light of virtually any color you might want from daylight thru orange to warm pink, search the web under "color temperature" for more info. How natural the light looks is covered by the CRI (color rendition index) of the tube, those with the highest CRI are 4 to 5 times more than cheap ones but we are talking about $12 versus $3.
In the U.S. the tubes are rated at 32 watts and to drive them get a thin-lite fitment or ballast (e.g. from Wind & Sun (model #153)) I have been bashing these real hard to see if I dare put them in a school in up river Gambia (Africa). So far they have tolerated all the abuse I have thrown at them, they are silent and pulse the tube at about 20khz so have no noticeable flicker after they have been on a for a few minutes.
They draw about 2.1 amps at 12.4 volts but tolerate a lot of variation. My experience is with using 36 watt tubes which seems to be all you can get in Europe (anyone in Europe know a source of 32 watt or 28 watt 4 foot tubes?). These only seem to put out about 2000 lumens when driven from a 12 volt battery but for 10' x 10' this is still quite a lot of light.
If you want to discharge your batteries no more than 20% in 6 hours (as recommended by this site) you need about a 60 AH (amp hour) battery. You do not say if your booth will be in use everyday, just at weekends or for occasional events. Either way I would be inclined to start by using an auto battery. If you really want to go bright just multiply up by the number of lights.