I'm building a website with a focus on searching so I want a very large search form in the header. I've been looking for a tutorial using Photoshop to create a background image to superimpose the search form on without much luck. Does anybody know where I can find one?
It seems that most designers just use CSS3.
I suspect you haven't found anything mostly because Photoshop is not where you'd normally create a search form. You can certainly make backgrounds, buttons and other style elements with Photoshop, but the form itself you'd create using Dreamweaver or your web development application of choice. If you're using a CMS like Wordpress or Joomla, the tools are built in.
Then you would use CSS to create the custom styling (size, position, appearance) of your form. Any of the Dreamweaver tutorials on lynda.com cover this. There's also a video by Greg Rewis on Adobe TV, from his "Taming the Web" series that covers creating and styling forms using Dreamweaver and Photoshop.
You might want to look at design patterns, search frameworks and their components that together create great search experiences to get an understanding of whats required and expected of great search functionality. Take a look at http://twigkit.com/components.html for examples.
I'd suggest that you understand what the technology you are designing for allows you to do and how willing the developers are at creating custom features or extending the code base they plan to use to get the best results.
