[keycloak-user] Dynamically branded login?

We build and host a multitenant application that is currently using homegrown authentication and authorization (using Picketlink). We are considering a move to Keycloak. My preference would be to use the login flows that are built in to Keycloak rather than building our own, however that is dependent on whether we can properly brand those login flows on a per-customer basis in some dynamic way. In looking at the theme SPI support, it appears to be mostly targeted to supporting mulitple "static" themes. Is it possible to make a theme that is dynamic based on, for example, a query parameter? Are there any examples anywhere on how that might be possible? Would Keycloak carry through query parameters if they were provided when launching the login flow? Thanks, Craig