Hi Nitzan,
Thanks for your feedback, enhancement requests are always appreciated! 🙂
To 1. - Thats already a pending enhancement, but in most cases this could be done by either stacking widgets (i.e. place an image widget behind another widget with transparent background). Or use a reference to the image as content of e.g. a cell widget or table cell.
To 2. - Its not possible yet to specify a style formula for pages, but I agree, that would be nice. In the meantime, for this purpose you could insert a widget with a style formula, referencing a central widget, and covering the whole page.
To 3. - Thats true and shouldn't be a big effort. Currently, once you have already one widget in the center of a page, you will see such red center-alignment lines for additional widgets (between the widget and the already centered widget).
Please let me know if you have any questions here, or if you need examples as an app file.
-hp