The parameters in Alex are tied to parameters...if you set them to none you can swap Alex with a different Render appearance, however he is of the People category and you will want the Plant category...I would recommend that you load a rpc plant (from the planting folder) and use that instead. Once it is loaded, select one of the families, edit and duplicate and change the type parameters as needed.
You generally have to buy additional images from ArchVision
https://knowledge.autodesk.com/support/revit-products/learn-explore/caas/CloudHelp/cloudhelp/2016/EN...
