I won't beat the topic into the bush, but, as everyone else has said, stealing is bad. Even if it's for personal use. If you're looking for free images, do a search for public domain images or check out
PDClipart.org - Public Domain Clip Art - they have a ton of images, quite a few of which are fairly close to printable.
Now, onto the question you asked
Is the image that you're using a small image that you are enlarging and is pixelating because of the enlargement process? If that's the case, my advice is to grab Adobe Illustrator (I believe you can get a 30 day trial for free still), place the image into a new document, and do an image trace. I won't go into a full set of instructions here, as there are plenty already on the web, but suffice it to say that this will enable you to enlarge the image without a drastic loss of quality.
I don't know if Corel Draw offers the Image Trace functionality, since I haven't touched a Corel product in half a decade or more, but if it does you may be able to accomplish the same thing.