<p>Instead of hanging a sheet, you could install a pull down projector screen (like we had in school in the 60s/70s). For the walls, a quick fix to warm it up and hide the block walls would be curtains. </p>
<p>Track hardware like this would allow you to install a long run of floor to ceiling curtains. If you can sew straight seams, you can buy a bolt of fabric and customize the length to suit your needs. </p>
<p>[Curtain</a> Tracks & Drapery Track Systems - Curtain Tracks](<a href=“http://www.curtain-tracks.com/]Curtain”>http://www.curtain-tracks.com/)</p>
<p>Ikea also stocks these rails, as well as some cheap panels.</p>