If you are looking to customize TLN (Top-Level Navigation) menu in Ajax Framework Page, then you have a configurable option to enable / disable images. This especially comes handy when you want to customize TLN menu and you are not able to find right set of icons for folder open and close. To be precise, these icons are called as Work Center Icons and their size is 71×48 px. If you have a graphic designer in your team or if you know someone who can get you these work center icons re-designed keeping in mind with organizational branding and colors, then perhaps you don’t need to worry about this configuration. Simply get new set of icons and upload from theme editor > Ajax Framework page > Top-Level Navigation > Work Center > Default image for work center & Down state for work center icon properties. However, if you do not have this privilege, then it is better to disable TLN Images and completely re-design TLN by customizing Ajax Framework Page.
To disable TLN Images, you have to navigate to Content Administration > Portal Display > Detail Level Navigation > Framework Page Configuration > Select Framework Page Name as “Ajax Framework Page (Ajax Portal Desktop)” as shown below.
At this point, you will find that all contextual properties are now available for configuration. Now, navigate to bottom of the page to Top Level Navigation section. There is a property called “Display Mode”. Set this property to “No Images” by selecting new value from drop down.