If you’re like many bloggers out there, you probably LOVE WordPress Twenty Eleven Theme, but you don’t want to look like an idiot (like I currently do with this blog) by keeping the default rotating header images that come with the theme.

You want to add a custom image, but you don’t want it to be a massive size like the 1000 x 288 pixel version installed by default.

This tutorial will show you how to add a new header image with the size of your choice.

Step 1: Make your new header image.  I recommend keeping the 1000 pixel width the same, but shrink the height down to 150 pixels or perhaps 125 or so.

Step 2: Go to your WordPress admin and click on Appearance/Editor.  You will want to edit the file called “functions.php” which is also titled Theme Functions.

Step 3: Look for or open with a text editor the following lines.  They start on line 120 if you use a text editor.

// The height and width of your custom header.

// Add a filter to twentyeleven_header_image_width and

twentyeleven_header_image_height to change these values.

define( 'HEADER_IMAGE_WIDTH', apply_filters('twentyeleven_header_image_width', 1000 ) );

define( 'HEADER_IMAGE_HEIGHT', apply_filters( 'twentyeleven_header_image_height', 288 ) );

Change the width (default set to 1000) to your desired width. Change the header image height from 288 to your desired height.

Step 4: Upload your new, custom header image by going to Appearance/Header and click save.

That’s it!  Your new header image will now show up as your blog masthead instead of the cheesy looking one.