Ah, sorry... I wasn't being sufficiently clear when I asked the questions, I think. The main reason why I asked those questions was to determine what sort of features you would need in a visual novel creation engine for your story. Then, we could suggest the engine that would best suit your needs. (Of course, it's very likely to be Ren'Py, but hey...

)
Based on your replies, I'm guessing the short and quick answer would be just to go with Ren'Py. However, if you want a longer, more detailed explanation of the reasoning for the questions, read below:
What I was thinking about in terms of storyline structure was really more of a programming issue. In what way will the user's choices affect the story? Is it a simple "choosing of one option from a list leads to a separate path in the story" (branching story), or is it "the cumulative sum of several choices you make along the way will determine which path you take." (variable-based story - think of Good-Evil alignments in RPGs to get an idea of what this means) Is it a straightforward "this is a block of text you don't interact with, and then comes a choice" (linear narrative with menu at the end), or is it structured like Wikipedia, where there are hyperlinks scattered throughout the text that leads you to a different spot?
Different engines have different strengths in those fields. For example, Ren'Py doesn't really support hypertext fiction structures, but Flash might. Likewise, Blade has problems with variable-based stories (if I'm not wrong... they may have upgraded it by now).
Likewise, for visual style, I wasn't really asking about artistic style, but more of directorial style. (Well, actually, a little of both...) What sort of visual or movement effects do you want? Zoom, pan, flash, snowflakes, multiple ways of transitioning from one image to another, etc.? Ren'Py is best suited for that. Do you have any particular need for being able to change your colour schemes, fonts, layouts and menu styles for the interface? Basically, how customisable do you want your presentation of the story to be? (In general, Ren'Py has the most customisable features, but it's also the most complex because of that. A simple story that doesn't depend much on visual style may be created on other VN engines just fine.)
BGM is all fine and good, but be careful which format it's encoded in (eg. MIDI, OGG, MP3, etc.). Certain engines will support some formats and not others. Likewise for movies. As for voice-acting, you can quite often get volunteers from the
Voice Acting Alliance community to audition for free. (Need to check with BCS for that, but I
think it was free...). And yeah, generally time and effort may not be worth having the extra polish of sound effects or movies (not to mention they eat up a lot of HDD space). That all depends on the story.
In any case, good luck with it, and hope you'll have something to show us soon.
-Dizzy-