[yorwba]

Just replace that /#/g with /[^\s]/g to replace all non-whitespace characters.

[aehtyb]

be forewarned that the reason it's asking you to use only #'s and spaces is the effect only works if the ascii image is very contrast-y. if the ascii art makes use of gradients (....:::;;;iiii@@@@) the effect won't be as obvious or work at all.

[skeoh]

Does [^\s] match anything \S doesn't?