This is possible in two ways:
1. Use Aspose.Words, see classes in the Aspose.Words.Viewer namespace to render images of pages. There are examples for this in Aspose.Words MSI download. The problem with this is viewer classes are Beta and will not render all documents nicely.
2. Use Aspose.Editor. Although it is a visual word processing control, you don't have to run it with a user interface. You can use the control to open a document programmatically and generate images (thumbnails) in any size, resolution and image type form it. There is a demo in Aspose.Editor download that shows that. The problem with that is Aspose.Editor does not support all word document elements yet, for example images and lists will not be rendered.
In any case, we are working on improving document to image capabilities in both products. So you can try now and if you don't like it, check back later in a few months.