Larger is the backdrop application to beat all others. Forget Acorn's Pinboard - Larger has far more features than any other program on the market. It's impossible to cover everything here, but...
Larger does everything Pinboard does, and its display is far neater. You can optionally display plinths behind icons on the backdrop for a professional look, and icons can be automatically organised (so applications and directories are forced to any side of the screen you wish). The backdrop acts like the Filer, with a similar menu structure, reducing the learning curve drastically. One excellent feature is the ability to create separate backdrops, which appear on the backdrop like iconised windows; double-clicking on a backdrop brings up a new layout, so you could have one backdrop for DTP, one forgraphics and so on. You can iconise windows in the usual way, and iconise all windows from one application.
The second major feature is the one that gives the application its name: it provides a virtual desktop. This increases the desktop so windows can be moved off-screen. To prevent you losing windows there is a map showing where other windows are at any one moment.
Calling it a sticky backdrop program hardly does it justice. For a tenner, this is one of those applications you can't afford to miss. If this doesn't become the de facto backdrop application, I'll eat my shorts.