writing design documents
Although professional graphics make a really nice impression, I think it's a mistake to invest a lot of time into getting professional mockups made for the basic specification phase.
Having some basic icons is good for maintaining an acceptable level of aesthetic appeal. However, having a single designer create realistic mockups for all of the pages is inefficient when when the design is still moderately fluid.
The page layout is still changing significantly, which means trashing entire pages of work. Also, we've only got one designer assigned to this part time, so I think it's unreasonable to have her do all the mockups. Also, any design changes have to be communicated to her so that she can adjust the mockups accordingly. We have six people writing specification documents and only one designer. It doesn't scale at all.