Stunner - Picture rendering performance improvements on canvas

When rendering pictures on the canvas, for example the bpmn icons for nodes on the contextual menu, each picture/icon is being handled as a (new) single image in the DOM, which is causing performance issues and results on some unnecessary delays for the end user.

For example consider the attached image - it shows what happens once just clicking on a node, so once the contextual menu is rending the icons for each button. Initially it renders as green rectangles until each image has been loaded and rendered into the canvas.

This does not happens on Chrome (Linux), but it's reproducible on FF, IE11 or Safari.