AnyChart JavaScript Gantt Chart allows you to replace default data grid collapse/expand buttons with custom image icons for a branded look.
This sample creates a project Gantt chart and styles the data-grid buttons by setting background fill images for the normal (close.png) and selected (open.png) states. Default button content is set to null so the images serve as the sole visual. The chart starts fully collapsed, then programmatically expands the "pre-planning" task to show the button states in action. The data-grid name column is widened to 280 pixels for readability.
See the Gantt Chart documentation for all configuration options.