You can already import PNG images with transparency (alpha channel) by dragging & dropping the PNG files onto your Adobe XD window, or by choosing File > Import. You can also bring individual Photoshop layers into XD by copying them in Photoshop and pasting in XD. Are you having trouble getting this to work? If so, please let us know the details.

Linking to external objects is not yet possible — if you add an image to your XD project, it will always be embedded in your .xd file. If you’d like to be able to keep image assets separate (linked), please upvote https://adobexd.uservoice.com/forums/353007/suggestions/12869109-linked-objects

Simple slide-in animations are already possible — for details check out this tutorial: https://helpx.adobe.com/experience-design/how-to/ui-prototyping.html. For more complex animations, please upvote https://adobexd.uservoice.com/forums/353007/suggestions/12869229-animation-support-microinteractions

I’m closing this feature request since it is a combination of things that should already be possible and things that have already been suggested individually. In the future, please help us keep the feature request list tidy by filing each different feature as a separate suggestion. If I’ve misunderstood anything, please reply back here or file a new separate bug or suggestion. Thanks for your feedback!