Hmm, not really; Brum city centre is pretty soulless (sadly).
I'd suggest a look in Wayland's Forge or Nostalgia & Comics if you're after something more hobby-related, but the smell (at least in WF) is, erm, powerful. There's also a GW store if you get *really* desperate...
You could also try having a coffee in the new library instead of in a chain shop; at least you have a nice building to look around that way.
If you're feeling up for it, the museum and art gallery are right in the centre too, and are easy to pop by and have a look around in.