We don't support image links with spaces in the name. So if you link an image in a markdown cell do it like this:

and don't do it like this:

Try to keep them under 15mb (our limit is 25mb), and make sure you don't have massive lists saved in the notebook somewhere - it's generally not helpful to the reader, and you can keep such data in a separate file.
While interactive javascript plots like Plotly and Bokeh do work (as well as associated client side widgets). IPyWidgets wont work as they require a running kernel - which Kyso does not provide (yet!!).