(define (mergeHelper L1 L2 acc)
  (if (and (null? L1) (null? L2)) acc
      (if (and (null? L1) (not (null? L2))) (mergeHelper L1 (cdr L2) (append acc (list (car L2))))
         (if (and (null? L2) (not (null? L1))) (mergeHelper (cdr L1) L2 (append acc (list (car L1))))
             (if (= (image-height (car L1)) (image-height (car L2)))
                 (if (< (image-width (car L1)) (image-width (car L2)))
                 (mergeHelper (cdr L1) L2 (append acc (list (car L1))))
                 (mergeHelper L1 (cdr L2) (append acc (list (car L2)))))
                 (if (< (image-height (car L1)) (image-height (car L2)))
                 (mergeHelper (cdr L1) L2 (append acc (list (car L1))))
                 (mergeHelper L1 (cdr L2) (append acc (list (car L2))))))))))