Ignore the below in blue - it's obviously been a while since I've put cutlines around a raster image - oops!
Maybe I misunderstood a bit - if you have a coloured raster image on a white background, for example, CorelDraw doesn't recognise the coloured image as such, it will only see the whole "tile", including the white background.
You will need to remove the background, and if you use another program to do so you'll need to export in a format from that program that works with transparancy, eg. .png.
The CorelDraw will ignore the transparent parts (!) and if you put a cutline around the image, it will no longer be just a box...
Having just put cut lines aroung a raster image in CorelDraw X7, I've realised that it is a much more complex operation than I remembered, and rather too complex to explain briefly in text, unless I've forgotten something - which is entirely possible!
I'll see what's available elsewhere and be back...
Later edit:-
The following youtube video pretty much mirrors the method that I use, though I don't reduce the image to black & white - though that may make the job a little easier with some images:-
https://www.youtube.com/watch?v=aabyoEe1grg