Whenever I encounter an undulating substrate sometimes the easiest way to correct the problem is to mix up some thinset on the stiff side and skim/float the weak area till it is on the proper plain with the surrounding area. It may take two or even three applications to accomplish but it is an effective method of surface preparation that is easy to control by using a 4' level to check the profile of your splash as it goes across the room. Ok Don I hope this helps you with your project, feel free to return anytime

You can refer to this blog which show you a article about kitchen backsplash ideas: design/remodeling
(if those website not change)

Kitchen backsplash ideas articles
http://kitchen-backsplash-ideas2.blogspot.com/

Simple Tips Kitchen Backsplash Ideas For Your House Articles
http://kitchen-backsplash-ideas2.blogspot.com/2009/05/simple-kitchen-backsplash-ideas-for.html

How to Make a Simple Kitchen BackSplash – Ideas For Your Home
http://kitchen-backsplash-ideas2.blogspot.com/2009_05_03_archive.html

Source(S)
Simple Kitchen backsplash ideas Blog
http://kitchen-backsplash-ideas2.blogspot.com/

Hope that helps!
Richard Man U