I'm not the most knowledgeable about Mer but as far as I know you can install anything that you can on Ubuntu. Of course the problem comes with hard drive space and computing power, so things like Gimp will run but slowly, on the other hand (unless something fantastic has happened) anything requiring 3D hardware support is a no go. To find what applications you can install you'll need to look at the Ubuntu repositories site. To install you need root access in xterm and then apt-get to install them. I hope I got all that right, someone should be along to correct me if not. Hope it helps