The key is to upload the widget itself (I call this - standalone widget) to the server of your page.
How to add your own landscape to YoWindow widget without crossdomain.xml.
1. Download standalone widget .zip archive from YoWindow website.
2. Unzip yowidget_standalone.zip
3. Upload the contents of yowidget_standalone.zip to your website over FTP in binary mode.
To the directory of your choice.
Find yowidget.swf file, it is right at the top level.
This is the main application file.
Remember the path to yowidget.swf.
4. Test if the standalone widget is working properly.
There is a test page - example.html - in the package.
Navigate to example.html and check if the widget displayed correctly.
5. Customize YoWindow widget on the setup page
6. Copy HTML code and paste into some text editor.
7. Replace the path "http://swf.yowindow.com/yowidget3.swf" to the path to yowidget.swf on your server.
You need to do this 2 times in the widget code.
8. Upload your landscape to your server.
WARNING: you must to convert .png image to .swf.
Otherwise your users are not to be happy.
9. Edit widget HTML code - add "landscape" variable to flashvars value.
Set landscape to the path of landscape .ywl on your server.
... &landscape=http://repkin.ru/yo/standalone/new_york_landscape/New York City.ywl"
10. Upload your HTML page to the server and check it out.
If you have made it right, you should see your picture inside YoWindow widget.