Decorating a shared bedroom

Jasmine and Sonny currently share a bedroom.  I say currently because that isn't the long-term plan, but it suits us for now.  They settle well together and enjoy the company.  One problem I have come across, however, is the issue of decoration.

Now, the room desperately needs decorating (and I mean desperately!), so the issue has become rather pressing.  How do we cater for the tastes of two children within one space?  Or, more precisely, how do we cater for two children of different genders within one space?

I've Googled it and marvelled at the creativity of others (I love the room pictured above, for example), but I'm having trouble marrying what I find with what my children like.

Sonny wants Thomas trains.

Jasmine wants Hello Kitty.

Hmmm.

Hubby says split it right down the middle, absolutely 50/50.  Paint half pink and half blue, give them a curtain each, their own carpet and shelves etc.  Like two completely separate rooms.

I see where he's coming from, but I'd still quite like there to be a neutral, shared theme. 

Right now, I'm thinking neutral carpet, pastel curtains, pale yellow walls, BUT give them one wall each.  One wall that can be any colour they choose, can have posters on, drawings, stickers, trains, anything.  Their own shelves, their name stencilled on, whatever they decide.  Thereby giving them a sense of their own space within a shared room.

But that's just me.  What would you do?