Hi Claire, Currently there is no 2D CWT implementation in the Wavelet Toolbox. The Shannon wavelet is a sinc in time so it does not have compact support. Accordingly, you cannot implement it with FIR filters. Frankly, I'm having difficulty even imagining how you could implement a decent 2D CWT approximation.
However, there is a FIR filter approximation for the Meyer wavelet, which is a similar sinc in time continuous wavelet. You can obtain and use those filters with
[LoD,HiD] = wfilters('dmey');
