At our school, the final major project done at the end of the year is called a CPT.
This is one of them
It involves building a giant letter (out of super cheap, recycled materials - BONUS!), and decorating it based on a "mentor artist" the student picks.
The final project is mixed media, and the sky is the limit with materials they can and do use.
This package involves
-An explanation of how to build the letters (out of toilet paper rolls, boxes, watercolour tape paper)
-A mentor artist sketchbook page / research report assignment
-A proposal (last 2 pages), complete with a timeline for the project
This takes them 3-4 weeks depending...they turn out FANTASTIC.
TIP - You can also assign the specific letters, so they can form words for display purposes. We did this for the library, and made really cool words/phrases to put above the library shelves.