Of interest to folks who craft ICA files by hand, or customize the ICA file template in Web Interface:an updated reference is now available of ICA file settings. I know there are folks who have been keenly awaiting this for some time. It is based on an exhaustive review of the 12.0 Windows client, with notes to reflect settings that are specific to some other clients (notably the Unix/Linux clients).
Please let us know if you spot any inaccuracies or deficiencies. (A number of old settings have been deprecated or classified as internal, and so are not documented.)
It is worth mentioning that many of the documented settings can be controlled through Group Policy and other systems that support registry configuration. Where it is appropriate to control them in this way, this is the preferred mechanism. The Group Policy template file ships with the ICA client itself, and its use is documented here: http://support.citrix.com/proddocs/index.jsp?topic=/online-plugin-120-windows/ica-import-icaclient-template-v2.html
It is also still the case that many settings can be controlled via the old .ini files that existed before Group Policy support was introduced in version 10.0. Officially most of these are deprecated, and may cease to be checked by the client in future, but I know it is still convenient for some customers who distribute modified .ini files in their own repackaged client installer.