textures are 1028x1028 x 32 bmp in order to dont impact the fps..
Well, not.
32 bit it's a very bad idea fot the fps, since they take about 6x the bandwidth to be transfered from system ram into video ram. That's the whole point of compressed textures: since the card understands DXT1/3/5 and decodes it in hardware, it's best to send them compressed over the bus.
Of course, 32 bit have a better quality, but the performance cost is probably not worth it, unless the scenery is *very* small so, you can afford sending 6x bigger images, since there are only a few of them anyway.
