I have my icons aligned top to bottom on the Default activity, however if I create a new activity it will be align left to right and I will have to manually change that. The same goes for the wallpaper and other settings. I would like to request a feature that would allow me to set these options globally across all activities.
At the moment Activities is basically feature-frozen while we figure out what we want to do with the feature, and what direction we want to take it in. Personally I'll be advocating for making this possible, but I'm afraid I can't promise anything specific.