The small subtle logo on the front is a big non-seller!
Actually, no offence but that's one of the reasons i haven't bought it yet.
To be quite blunt: it's dull.

To go on use my creditcard for a t-shirt that has to be shipped from England to good old Holland with a logo like that isn't what i had in mind.
It's not adventurous simply because the t-shirt isn't adventurous.
When you want people to order many, and i say many T-shirts it has to be a bit more colourful than that. An (previous) album-print on it, indeed like the already mentioned snippets of lyrics of Arena songs, tour dates might work but only if you come up with a new t-shirt for the next tour. (yes, i know were talking about it here but it was just an example)
I'm even a bit surprised that you didn't use the album cover of Ten Years On for the previous (little) tour.
I didn't went to the concert, sorry bout that since i was a bit busy last year to say the least but i definitely ordered something like that on the online store.
No offence of course.
So.... a black T-shirt WITHOUT a large rubber square on the front.... good plan! Something more than a little logo though...
Maybe the dates on the back, but I like the idea of something else... lyrics, design, or some kind of statement...
But what should the artwork be? This isn't a Pepper's Ghost tour.....
Maybe something like a 'best-off' shirt(Ten Years On)? Some pieces from the previous albums or some tiny reminders of the likes. A roaring lion with in the back a picture of the old bike of the Visitor etc etc.
Dream Theater did something like that during the previous tour (octavarium) in an octagonal showing all DT's albums.
By the way: i'm rather tired so excuse me for some direct words.

Edit: This reminds me of a tiny question: What kind of tour is it then? A follow up of the Ten Years tour or a preparation for the new album?