If you can I´d paint the bar and the other black furniture to cheer it a little up. I´d also change the cussions on the sofa. maybe white with green stripes?
Are you allowed to paint the walls? What about one bright stripe, maybe in clear white or cherry-blossom-pink? And than you can work with that... what about working out a color palette?

I think that three paintings or drawings in the formats and positions below would look good. I agree with Varonjy that different cushions could liven things up and you could take colours from the art to help you create your palette. The bar is far too crowded and the flowers definitely don't belong there. I suggest you place no more than five of your most attractive bottles on it, clustered to one side in a group, and place something like a pretty decanter to the other side. Bring everything in a few inches from the edge. You might consider hanging a pretty, purely decorative mirror above the bar on either wall -- though I'd like to see drapes on the window, in which case the mirror (or something else) should go on the left wall. By purely decorative, I mean that it acts as a shiny object to work with the glass bottles, rather than being hung to reflect anything in particular. This one is from http://www.overstock.com/Home-Garden/Mirrors/Square,/mirror-shape,/2009/subcat.html.