I take “generalized links” to mean links to other products…” to mean links to other products which give a general idea of what your proposed product will be like. Instead, send images of your actual product.
Of course, literally, a link cannot be generalized—a link is a specific address, but “generalized” really refers to the nature of the target of the link, which is a page or image which represents a generalized idea of the product concept. The phrase is rather loosely worded, grammatically, but this sort of thing is quite common in English.
You can actually take this to mean do not send any links to other products for the purposes of illustrating your product idea.