Thank you Sebastian.204 and AFRLme for your feedback.
@Sebastian.204: I was interested in knowing whether (apart the restrictions you pointed out) there was a difference in the code version between the free and the for sale version of the editor.
In order to (hopefully) reduce the load and the processing I have decreased my game resolution down to 1280x720. So my 4x scene is now 5120x720 png (I gather Visionaire has been thought for 3x scenes tops, but I did fancied to have an effect similar to sam and max game while they are walking on a sidewalk).
- I generated a 5120x720 transparent png
- I chopped my background image in 16 tiles (640x360 each)
I started placing the tiles and after placing 4 of them I tried to save my work. An unhandled exception was raised and then a popup "Saving ved file..." appeared; but it got stuck after a couple of seconds (the green progressing bar was very little) and after killing the process the work done was lost.
So I think I am going to change my plans now, by subdividing my 4x scene in two 2x's, as you seem to advise. I guess it is no longer advised using the tiling for 2x backgrounds, is it right? (I mean I can just load the 2x images as different scenes)?