I have been able to set higher resolution by editing the option value in html code.
Now when I take photo with camera it takes images in 1280x1024.
But I still have problems with video streaming, could it be that mi Rasp1 is not powerful enough to stream an higher resolution video?
If i set camera in low res, both pictures and video work just fine
If the problem comes from a rasp1 not enough powerful, it could be a solution to split image resolution in 2 sections: video and pictures.