If it's for a specific role you want to hide them, then you can use UI Personalization > Adminstration > CMS > Media Dialog > (Uncheck those that should not be shown)
If it's just for THIS particular tool you want to hide those, but still allow the user to get at the other spots, then that would involve modifying the CKEditor configuration in the /CMSAdminControls/CKEditor (/CMSAdminControls/CKEditor/plugins/CMSPlugins/plugin.js, may want to prettify it)
pluginInsertImageOrMedia: function(e) {
var t = "InsertImageOrMedia",
i = {
exec: function(e) {
var t = window.unescape(e.config.MediaDialogWidth),
i = window.unescape(e.config.MediaDialogHeight);
CMSPlugin.currentEditor = e, CMSPlugin.openModalDialog(e.config.MediaDialogURL, "imageormedia", t, i)
}
},
You would have to try to find where the e.config.MediaDialogUrl is located and adjust it to point to a custom URL or append the parameters that would limit the items show.