There are two file size limits when publishing a Lens. The first is the 8MB limit which is the compressed file size. The other is the 20MB limit for when the Lens is uncompressed. Typically the two are pretty close in size but animated textures and large groups of textures have an outsized impact on the unpacked file size.
Our general guidance is to use lower quality textures and to reuse the same textures where possible to limit the number of textures in use.
One quick workaround is to change the compression of your textures to optimize for size. This will however result in higher RAM usage which could impact your Lens' ability to pass review.