I played a bit with a Jessie VM and E17/LXDE.

In E17 I thought autohiding the shelf of the mobile theme might be useful to gain some additional space.
But this shelf can't be hidden since it's no regular shelf. Instead it's a special module called "illume-home". So I disabled the illume-home module alltogether and created a regular shelf that autohides in its place.
Surely no revolutionary change, but maybe a nice side note.

btw: Does someone know how to configure which icons should be shown on the E17 desktop (other than wreaking havoc in /usr/share/applications)?

As for LXDE I tried Estel's suggestions and found my first result quite pleasing (for someone who often earned facepalms from his art teacher). - screenshot attached
The top panel is autohiding, so is the (currently invisible) bottom panel that contains a task bar.
The ugly [X] in the upper right corner is a starter wmctrl to close the currently active window (yes, heavily "inspired" by bodhi-close), making the window's title bar pretty much useless.
The browser is qupzilla with the window bar disabled while the url and menu bars are temporarilly hidden underneath the lxpanel.

@Estel (or someone else who knows):
Is there a way in openbox to undecorate (disable title bar) all windows by default and permanently?

This is the wmctrl starter (I simply copied and adapted the leafpad file, which explains the quite pointless "Categories" line):At the moment I'm quite torn between E17 and LXDE. E17 sure has the looks and I like it how you can adjust the delay before a shelf autohides. On the other hand LXDE has the stability (E17's file manager always crashes when I try to open a file) and seems to be a little bit faster.