I have confession to make. Two points, I must admit that:

• I have not found an image viewer that I like in Ubuntu, I found they feel clumsy to use (or is it me?) I tried Mirage, Eye of Gnome. Honestly I'm not going to spend any more time installing and trying out every image viewer out there.
  
• my favorite freeware image viewer is FastStone, ACDsee is a little better, IMHO, but it's not free, so no thanks :)
  

OK I said that, what's the solution?

Thankfully we have Wine. I installed FastStone 3.7 in Wine 1.1.14 on Ubuntu 8.10 and it works like in real Windows with some little quirks. But over all it's usable, very usable.
Want a proof? Here's my screenshot. I deliberately put Wine window over FastStone window so there's no doubt that this is Linux (Ubuntu) indeed.

How to install FastStone on Ubuntu?

• First you need Wine installed on your system, you can find it in Synaptic Package Manager - search for Wine,
  
• then you can install FastStone like you would under Windows.

Little tips :

To make the scroll mouse works in the fullscreen mode, you may have to press Esc key once (and only once for the first time you use it).
There's a little quirk when you minimize the application, and then maximize it again, try click it twice, if it won't maximize.

Notes :
I've tried FastStone 3.2, 3.6 and 3.7, all work.


keyword : image viewer in ubuntu, wine, faststone