PS: I have done the courses (pre-req), so the question is specifically for preparation material and previous questions etc..
You could take a look at the description for the Architect Certification Lab
As of 16-Sep-2013, the description says
Installation and Infrastructure
- Install a search head, deployment server and indexers
- Perform a scripted installation of universal forwarders
Configuration, Collection, and Comprehension
- Deploy all specified configurations via deployment server
- Gather data from forwarders and send to multiple indexes depending on use case
- Configure and confirm index-time knowledge
- Create search time field extractions
Searching and Reporting
- Create searches and dashboards for each required use case
Since this is a practicum and not a multiple-choice test, you need to be able to do these things, not answer questions. During the exam, you will be able to access documentation and answers.splunk.com
Practice doing the tasks that you learned in class - setting up indexers, using the deployment server, creating indexes, etc.
Publishing any detailed scenario is giving too much away.