Conventional (t, n) secret image sharing schemes share a secret image to n shared images, where any t shared images recovers the secret image. Among these shared images, noise-like properties easily draw attacker attention. Embedding shared images in meaningful cover images thus efficiently reduces attacker attention. This paper presents a different-expansion technique based invertible secret image sharing scheme that allows participants to perfectly restore the secret image and cover images. The proposed scheme also contains a lossy property which means that cover images do not have to be perfectly recovered to share larger secret images. The proposed scheme performs well with M-ary number systems, allowing users to determine the trade-off between covered image quality and secret image size. Experimental results show that the proposed scheme shares a large secret image and has good covered image quality.