I think that Tarvek is actually Van Rijn.
He has been interested in Van Rijn and the Muses since he was a kid, and has been a dedicated student of RvR's legacy. He was able to successfully reverse engineer Tinka and create an impressive parody with Anevka. He was thrilled when he came across Van Rijn's notes, and they obviously inspired him to new levels.
Given Tarvek's facination, I think that if/when Agatha and co. get a Time Travel device, he may attempt to go back in time to meet Van Rijn and/or his ancestor, Andronicus Valois. Upon arriving in the past, he might discover that as of yet, Van Rijn does not actually exist. He then would assume the identity himself and undertake the construction of the Muses.
According to the Clockwork Princess novel, little is actually known about Van Rijn's childhood, though he claims to be from the Dutch kingdoms. He has also gone to great lengths to ensure that a portait was never made of himself, and generally obscure his past and personal information.
If Tarvek were Van Rijn, then that would explain why so little is known about his background, and why he went through such trouble to keep it that way; It might not be good if people noticed that the young Prince Stermvoraus looked exactly like the famous Spark from 200 years ago.
Finally, there are the muses themselves. No one has ever been able to replicate them in 200 years, but it's possible that the technology was just 200 years ahead of its time. Also, you must admit that Tarvek has a thing for elegance and finesse, and the Muses are famous for their structural finesse.
Also they have very nice outfits, and he likes to play with dolls.
One interesting thing about htis theory is that it would invoke the Information from nowhere paradox. Tarvek has always been interested in Van Rijn's work, and so goes back in time to meet him, thus discovering that he is him. HeterodyneGirl (talk) 23:24, September 25, 2012 (UTC)