Below, I've included links to the audio clips of one-chord songs at different speeds you can use to practice strumming.
Chain of Fools - Use C5 or C minor chords to play with these audio clips. Any strum pattern could work, but #3 and 4 sound good. For a challenge, chain (pun intended) 3 and 4 together for an 8 beat-long pattern.
Lime and the Coconut - Use C or C7 to play with these audio clips. Any strum pattern could work, but #5 and 6 sound good. For a challenge, chain 5 and 6 together for an 8 beat-long pattern.
The Beat Goes On - Use F to play these audio clips. Any strum pattern could work, but all patterns should have a swung or shuffle feel to them. Try #3 and #10 (ghost pattern). You could even try a LONGER 8-beat pattern of ... (see below)
D D D DU | -U D D D
1 2 3 4& | -& 6 7 8
Low Rider - Use G to play these audio clips. Any strum pattern could work, but try #1 and 2.
Music (by Madonna) - Use F# minor to play these audio clips. Any strum pattern could work, but try the two here. You could even try a LONGER 8-beat pattern by combining the two.