Plan your instructional approaches in such a way that you could not proceed without the use of significant wall space for visuals.
Use the energy of students to create many of them–especially in middle grades and up. Post changing displays of student work: illustrated vocabulary words, penmanship samples, neatly done math work, book reports, posters…
Post time lines, maps, photos of people and places. Post charts showing concepts such as place value or types of levers. Create worksheets that require students to use wall material for their completion.
Post riddles, poems, brain teasers, news tidbits, “did you know” facts. Consider having students responsible for weekly changing displays of one or more of these.
Consider an activity section, such as a giant crossword puzzle (perhaps student made).