Well, this doesn't specifically have suggestions, but Sepulchrave II's Story Hours are one of the finest examples of high level play and just DAMM fine storytelling. One of the main characters is Mostin The Metagnostic (alienist), for specific ideas you'll want to check out the Rape of Morne and Wyre Part II sections, since they are around the time when Mostin hits epic.
http://enworld.cyberstreet.com/showthread.php?s=&threadid=5652&perpage=40&pagenumber=1
This is the Rogue's Gallery for the story hour and has many examples of epic level creatures. There is also one poster who has links to all the story hours in there and they are -
Lady Despina's Virtue I, Lady Despina's Virtue II, The Heretic of Wyre, The Heretic of Wyre II, The Rape of Morne, The Rape of Morne II, Eadric and his Friends
Finally, the ELH does have an Epic level Pseudonatural template, that is far more powerful than the T&B version. I would guess that part of the epic level progression for an alienist would be either gaining bits and pieces of the template for summoned creatures as progressing or as a 10th lvl ability.
Since much of what an alienist is about is summoning, perhaps a wider selection of more powerful (pseudonatural) creatures, would also be in order?