I back no rug too - and may I make another suggestion, budget permitting? Consider getting lined AND interlined Roman blinds instead of curtains for the window. It's a very tall room but seemingly a bit "chimney-like" because of its proportions. The tall thin curtains reinforce that feeling. Some wall mounted shelves from IKEA would be a great replacement for the somewhat random bookcase too. Rug might work then with a blind and wall-mounted shelving.....

I think you feel it looks too solid is because you haven’t followed through with the rest of the room, for example cushions to tie in with it. Further up these comments minnie101 has suggested some black patterned cushions which i think would lift the scheme, however if you really don’t like it then follow your heart and return it. Why keep something you don’t like? Then choose a colour-way that you prefer, such as the blue you suggested. A blue coastal theme would tie in nicely with the neutral theme you have at the moment. By the way, i got a Turkish rug from Olney Carpets in Bucks, and they let us take it home for a week to see if we liked it before buying! True service, and yes we did buy it! Of course buying online does give you that option too. I wish you lots of luck.

Presuming you are keeping the colour scheme the same anything from a Black, Slate or Silver Plush at the top end to more affordable Santa Cruz Boardwalk if you want more than one colour and more affordable.

Well I did actually go and buy one and what a difference it made! Couldn’t get the one I wanted in the larger size from the link you posted (all out of stock!) but I did buy one from another company who are eco friendly and make theirs from plastic straws as well. Was going for a grey one but decided on something vibrant to brighten the concrete base up and we love it! It’s huge though.