To change the default color of the Tab-Bar

Add the below code in viewWillAppear of your class

CGRect frame =

CGRectMake(0.0, 0.0,self.view.bounds.size.width, 48);

UIView *v = [[UIView alloc] initWithFrame:frame];

[v setBackgroundColor:[UIColor colorWithRed:0.1 green:0.2 blue:0.6 alpha:0.8]];

[v setAlpha:0.5];

[[self.tabBarController tabBar] insertSubview:v atIndex:0];

[v release];

And we can also image pattern color.

 UIImage *i = [UIImage imageNamed:@"abc.png"];

 UIColor *c = [[UIColor alloc] initWithPatternImage:i];

And we can also place image in tabbar background.

CGRect frame =

CGRectMake(0.0, 0.0,self.view.bounds.size.width, 48);

UIImageView *v = [[UIImageView alloc] initWithFrame:frame];

[v setImage:[UIImage imageNamed:@”YOUR IMAGE NAME”]];

[v setAlpha:0.5];

[[self.tabBarController tabBar] insertSubview:v atIndex:0];

[v release];