Setting a background image for a tabbar

You can use custom class for UITabBarController & override your tabBarController. There you can set your required buttons & their actions with image.

This is how your custom tab bar controller class can be look like:

// CustomTabBarController.h

#import <UIKit/UIKit.h>

@interface CustomTabBarController : UITabBarController {
    UIButton *settingsButton;
    UIButton *infoButton;
    UIButton *aboutUsButton;
}

@property (nonatomic, retain) UIButton *settingsButton;
@property (nonatomic, retain) UIButton *infoButton;
@property (nonatomic, retain) UIButton *aboutUsButton;

-(void) addCustomElements;
-(void) selectTab:(int)tabID;

@end

// CustomTabBarController.m

#import "CustomTabBarController.h"

@implementation CustomTabBarController

@synthesize settingsButton, infoButton, aboutUsButton;

- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];


}
-(void)viewDidLoad
{
    [super viewDidLoad];
    [self addCustomElements];
}

-(void)addCustomElements
{
    // Background
    UIImageView* bgView = [[[UIImageView alloc] initWithImage:[UIImage imageNamed:@"tabBarBackground.png"]] autorelease];
    bgView.frame = CGRectMake(0, 420, 320, 60);
    [self.view addSubview:bgView];

    // Initialise our two images
    UIImage *btnImage = [UIImage imageNamed:@"settings.png"];
    UIImage *btnImageSelected = [UIImage imageNamed:@"settingsSelected.png"];

    self.settingsButton = [UIButton buttonWithType:UIButtonTypeCustom]; //Setup the button
    settingsButton.frame = CGRectMake(10, 426, 100, 54); // Set the frame (size and position) of the button)
    [settingsButton setBackgroundImage:btnImage forState:UIControlStateNormal]; // Set the image for the normal state of the button
    [settingsButton setBackgroundImage:btnImageSelected forState:UIControlStateHighlighted]; // Set the image for the selected state of the button
    [settingsButton setBackgroundImage:btnImageSelected forState:UIControlStateSelected]; // Set the image for the selected state of the button
    [settingsButton setBackgroundImage:btnImageSelected forState:UIControlStateDisabled];
    [settingsButton setImage:btnImageSelected forState:(UIControlStateHighlighted|UIControlStateSelected)];
    [settingsButton setTag:101]; // Assign the button a "tag" so when our "click" event is called we know which button was pressed.
    [settingsButton setSelected:true]; // Set this button as selected (we will select the others to false as we only want Tab 1 to be selected initially

    // Now we repeat the process for the other buttons
    btnImage = [UIImage imageNamed:@"info.png"];
    btnImageSelected = [UIImage imageNamed:@"infoSelected.png"];
    self.infoButton = [UIButton buttonWithType:UIButtonTypeCustom];
    infoButton.frame = CGRectMake(110, 426, 100, 54);
    [infoButton setBackgroundImage:btnImage forState:UIControlStateNormal];
    [infoButton setBackgroundImage:btnImageSelected forState:UIControlStateSelected];
    [infoButton setBackgroundImage:btnImageSelected forState:UIControlStateHighlighted];
    [infoButton setImage:btnImageSelected forState:(UIControlStateHighlighted|UIControlStateSelected)];

    [infoButton setTag:102];

    btnImage = [UIImage imageNamed:@"aboutUs.png"];
    btnImageSelected = [UIImage imageNamed:@"aboutUsSelected.png"];
    self.aboutUsButton = [UIButton buttonWithType:UIButtonTypeCustom];
    aboutUsButton.frame = CGRectMake(210, 426, 100, 54);
    [aboutUsButton setBackgroundImage:btnImage forState:UIControlStateNormal];
    [aboutUsButton setBackgroundImage:btnImageSelected forState:UIControlStateSelected];
    [aboutUsButton setBackgroundImage:btnImageSelected forState:UIControlStateHighlighted];
    [aboutUsButton setImage:btnImageSelected forState:(UIControlStateHighlighted|UIControlStateSelected)];

    [aboutUsButton setTag:103];

    // Add my new buttons to the view
    [self.view addSubview:settingsButton];
    [self.view addSubview:infoButton];
    [self.view addSubview:aboutUsButton];

    // Setup event handlers so that the buttonClicked method will respond to the touch up inside event.
    [settingsButton addTarget:self action:@selector(buttonClicked:) forControlEvents:UIControlEventTouchUpInside];
    [infoButton addTarget:self action:@selector(buttonClicked:) forControlEvents:UIControlEventTouchUpInside];
    [aboutUsButton addTarget:self action:@selector(buttonClicked:) forControlEvents:UIControlEventTouchUpInside];
}

- (void)buttonClicked:(id)sender
{
    int tagNum = [sender tag];
    [self selectTab:tagNum];
}

- (void)selectTab:(int)tabID
{
    switch(tabID)
    {
        case 101:
            [settingsButton setSelected:true];
            [infoButton setSelected:false];
            [aboutUsButton setSelected:false];
            break;
        case 102:
            [settingsButton setSelected:false];
            [infoButton setSelected:true];
            [aboutUsButton setSelected:false];
            break;
        case 103:
            [settingsButton setSelected:false];
            [infoButton setSelected:false];
            [aboutUsButton setSelected:true];
            break;
    }   
    self.selectedIndex = tabID;
}

- (void)dealloc {
    [settingsButton release];
    [infoButton release];
    [aboutUsButton release];

    [super dealloc];
}

@end

Hope this will help you a lot.