New this build: icons in autocomplete lists! This shows icons for every item in the autocomplete list, showing either its object icon (or the system icon for system expressions), variable icons, or behavior icons. This should make it easier to differentiate between things like system expressions and global variables in the autocomplete lists, as well as providing a handy visual reference. Below is a screenshot of what it looks like.
There's also a new ImageMemoryUsage system expression, which returns the estimated memory usage of the currently loaded images. This is only supported in the WebGL renderer, since that's the only one we actually have control over memory management in (canvas2D games will return 0 for the expression). Also note that the export-time automatic spritesheeting will affect this value - so it will be more accurate after exporting than in preview mode - and it's only an estimate, not taking in to account other applications, system resources, or power-of-two size allocation by the GPU. So to avoid being caught out by its inaccuracies, be sure to come in under your memory budget.