In new brand Photoshop CC 2015, adding artboards in one psd is now possible. Is there anyone who knows how to combine existing multiple psd files as artboards in one psd file in Photoshop CC 2015?
File > New and choose
Artboard from the document type.
Load the images as layers.. then
Layer > New > Artboard from layers
Or just choose
Layer > New > Artboard then place your external files on the artboards.
You may want to check the new feature movies... https://helpx.adobe.com/photoshop/how-to/design-with-artboards.html