Whats a great thing to have in the lobby?  

Verner Panton System 1-2-3 chairs with the premium tufted leather upholstery perhaps.  
But I am afraid the better answer is more chesterfields.

Photos of the space would certainly help.  Are you looking to go more contemporary / modern?

Grey carpets and blue walls doesn't strike me as the natural enviroment for chesterfields.
I had Chesterfield sofas once, and I have to agree with Leif. If you choose to have chesterfields you have to go "all-in"
When I got mine into the livingroom, I quickly realised that I had to change my coffeetable, diningtable, chairs easy chairs, bookshelfs and sideboard since none of them where in mahogany. Yes mahogany. Not rosewood (too flamboyant). Not teak (too middleclass for chesterfield) MAHOGANY. If you go totally crazy and live your life on the edge, maybe you would dare to put in an oak drawer.
After that I realized that I needed to have some carpets (in a dark red pattern) and, of course, mahogany panels at the walls.
The only thing I had that matched, was a kerosenelamp with a green glas pendant.
I chose to sell the chesterfields.
This is not meant to discourage you. It's just my personal experience with chesterfield. If you have the budget for it, go nuts. Chesterfields do look good if you have the room for it.
P.S.
Almost forgot. A fireplace. Very important. You got to have a fireplace, with som wooden logs at the side (doesn't have to be mahogany)

May I suggest a well-stocked bar?
And a bartender worth his/her salt.  I believe those would go nicely with Chesterfield sofas, grey carpets, blue walls, and a fireplace.

Maja,
I suggest this professional staff to welcome your guest and constantly re-arrange the furnishings.  I highly recommend these three indivduals.  Their unique style and high energy work ethic will make them a positive part of your growing team of industry leaders.  
They do not drink too much and they will eat "pretty much" anything you give them.  Wild hyacinth is not recommended.
 
 

Hi Maja,
If the inside of your hostel is as nice as the outside then consider yourself lucky with a perfect opportunity.You cannot beat starting off with an ornate heritage interior space.
While the Chesterfields do need a bit of space for scale they can look hot with many styles.Forget this idea about strictly old world charm that first comes to mind.I would recommend to go straight to eclectic,funky and fabulous.
The first image is one of my favourites but you should get my drift.I am not in design and no expert but I would paint the place first,place the Chesterfields and work from there.Rug,coffee table and work outwards type thing.
Don't rush to buy stuff and remember an old chair or wooden box found on the street is better and has more character than anything from Ikea or the like.If many pieces are old you should throw in something super contemporary and or colourful for impact and some good size plants.
Don't forget we appreciate images on DA and would like to see your final look once done.

Ok now that I'm getting excited about some hot Chesterfield action here are a few more to get the blood flowing.Drooool!
The first 2 amazing spaces are in Brazil which is no surprise and the modern Chesterfield type sofa is called Otto by Guilherme Torres.

Very nice. Loved it!