How scary should a calendar be?
3
Providing thumbnails
My World and similar software packages usually save the artwork produced as either GIF, BMP or JPEG files. If you wish to produce a sheet with all the 12 monsters on it, you can easily do this using a DTP (Desk Top Publishing) package. 
Draw a grid for the 12 months. Then just import/place each month's picture in turn and shrink it to the size of the appropriate slot on the grid. Then you can print out all 12 at once.
The "12 all on one sheet" is a useful way of helping small group discussion about the work of the whole class. Divide the class into 6 groups; give each group a sheet and ask them to compare the images and explain to one another why they find some more attractive than others. You can also use the "12 all on one sheet" as the back of a letter to parents in which you explain about the work your class is doing in design & technology.