Stick with me here....
So now that this event has grown so much and has much bigger guests, perhaps discussing all these small tweaks is a false economy, maybe it's time to re-evaluate all together. I am not a convention goer per se but I do go to a lot of large sports events, business conventions and concerts. This - and I mean to with genuine respect - seemed to be out of its depth - and the lack of organisation and 'professional' tips and tricks weren't obvious (signs, queue management, flow plans, rest spaces etc).
I can imagine that once there was quite a distinct type of audience; those who are die hard fans and really treasure collecting autographs and photos with creative artists, mixed in with some first timers and one off fans of particular shows like Star Wars/Star Trek etc. The business model (and although I have no doubt the organisers are all big fans too it IS a business and there's nothing wrong with that) seems misplaced.
But with the stature and number of guests now it is attracting a very large and very broad spectrum of attendees; many of who probably have no desire for autographs of the 'third stormtrooper on the left in the second scene'......but it would be a incredible to meet/see stars like Carrie Fisher or John Hurt in person. They are also people who probably don't buy a lot of stuff in advance and bring their children and family along. But in reality what do they have to do when they get to the convention? Too late/too difficult to get VTs for the big stars, exhaust a picture or two with regular stalwarts but icons like Dave Prowse, admire some of the costumes?.....but then what? Nowhere to go, do or stand except get in the way of the stalls or auto/photo lines before leaving 90 mins later having had 'a nice day out'. Because that was me on Sunday.
Forget the little tweaks, perhaps it's time to think BIGGER! Get a bigger venue for a start, but put on more shows/screenings/talks, cosplay runways/EVENTS etc. Apart from the standard business of Autos/photos, attract people in who will make money on the door or buy merchandise etc but not necessarily interested in 15 autos and 10 photo shoots, and give them something to do and enjoy AWAY from the more busier 'business' areas - get Carrie up to do a quick Q&A for them on stage and they'll be happy etc.
Create some 'rest' spaces here too, as well as food areas. That way you keep the autograph and photo areas CLEARER which allows more opportunity for queue and ticket management; much of which - but not all - should be pre-paid. Less stress all round. You must know roughly how many autos can be signed and photos taken in a time slot so sell them in advance for the bigger guests. Someone said that you offer more VTs than viable as some will not show up, well I bet they will if they paid, and you don't lose income. Keep the not-as-big stars in another area and available for walk ups - much as it was this weekend.
Then look at the functional tweaks - restrictions on multiple 'dealer' signings (or organise specialist after hours sessions), eTickets, larger visible signage, tannoy/electronic signage updates hand out guides/floor plans on entry, more info points etc. Many great ideas in posts above.
Finally, one clearly cannot please everyone, there needs to be some expectation management for guests, visitors and organisers alike, but that shouldn't mean the vast majority will get what they individually want out of it whether that's a nice profit, a fully signed ROTJ poster and photo with Carrie (and the 3rd stormtrooper on the left...of course ), or a great day out with the family.
Just my tuppence.