here is a simple way to customize the UISlider images
UIImage *stetchLeftTrack = [[UIImage imageNamed:@"left-slide.png"]
stretchableImageWithLeftCapWidth:10.0 topCapHeight:0.0];
UIImage *stetchRightTrack = [[UIImage imageNamed:@"right-slide.png"]
stretchableImageWithLeftCapWidth:10.0 topCapHeight:0.0];
[sldDistanceFilter setThumbImage: [UIImage imageNamed:@"slider_ball.png"] forState:UIControlStateNormal];
[sldDistanceFilter setMinimumTrackImage:stetchLeftTrack forState:UIControlStateNormal];
[sldDistanceFilter setMaximumTrackImage:stetchRightTrack forState:UIControlStateNormal];
You just need to replace the image names according to your suite.