I imagine Anakin - as a fourteen-year-old teenager, before Obi-Wan takes him as his apprentice - as looking rather lean, clean-shaven, with longish blond hair, in white/gray clothes similar to Luke's in ANH. Later, as a Jedi in his 20s, I see him more refined, with neater, combed hair and a simple close-fitting black outfit like Luke's in ROTJ, but with an overall similar lean physique. As an older man, though, in his 40s, I see him as heavier, with more muscle/fat, and more rugged; his hair is closely cropped, his skin weathered and scarred in places, he goes unshaven, and he wears heavy dark clothing reminiscent of Exar Kun's and Ulic Qel-Droma's robes. In every variation, I see Anakin played by Leonardo DiCaprio.

With Obi-Wan, as a young twenty-year-old man, just before he meets Anakin, I imagine him as he is pictured in most of the TPM concept art, with long black hair, in black robes, and clean shaven. As the years go by, Obi-Wan begins to look more and more like his ANH self, growing a beard as his hair grows shorter and grayer. I still picture Ewan MacGregor as the younger Obi-Wan.

I picture Mother Skywalker (Anakin's wife, not mother, BTW) as looking like a young Jane Fonda with red hair. I imagine her to have a rather innocent demeanor.

Palpatine I picture as a young, passionate, charismatic man, in his late 20s-early 30s, who seems to radiate with confidence. I picture him to look a lot like Gaspard Ulliel, but with blonde hair and blue eyes.

Mace Windu I see as being the same aloof prick he is in the films, but played by Djimon Hounsou rather than Sam Jackson.