Get your MIDI controller, you can upgrade to Home Network later. Just send an email to Winstep support.
If you want to distribute your own themes, feel free, but anything that wasn't made by you and you want to include on a theme you must ask permission from the original author first. If it's only for personal use, you can do whatever you want.
You can add a background to existing themes that do not have a background. Just save the file as 'wallpaper.jpg' or 'wallpaper.png'.
You should wait for the upcoming Winstep Theme Builder if you want to make your own stuff, though, otherwise you will have to learn about editing configuration files, what all the settings do, etc... very time consuming.
To save a given set-up for a given theme, you can use 'Backup Workshelf' and 'Backup NextSTART' (if using Xtreme), and alter the file names to something easily identifiable (not the extension though, i.e., .wbk and .nbk!). The theme itself (which is basically all the gfx etc.) will also have to be saved separately - simply copy all the theme's files from its folder in C:\Users\Public\Documents\Winstep\Themes and zip them up, giving the zip file the same name as the theme. Copy this zip file to the intended machine's C:\Users\Public\Documents\Winstep\Autoinstall folder, and the respective .wbk and .nbk files to the intended machine's C:\Users\Public\Documents\Winstep\Backups folder. Go to the destination system (use remote desktop if you can), start up Winstep - which will then automagically install the theme - and then in Workshelf use 'Restore WS' and then in NextSTART use 'Restore NS' and this will restore all the saved settings.