For most you'd be advertising what some people may feel are your competition, also Pagerank comes into play. If someones worked hard to get a PR or 4 or 5 they won't want to exchange links with a PR 1 or 2 site as it would bring there's down.
I don't mind putting a link for you on my design site. But the only way it would help either is if someone found your site looking for design and they were based in my area or someone found my site and wanted something from your area. Believe it or not in the age of technology people still seem to keep their work pretty local.
The most important form of
SEO is not links in or out but how the SE reads the site. ie how it's built, robot.txt H1-H6 headers, regular updated content and clever keyword density.
Hope this helps and I'll add you a link if you pm me what the text link has to say (remember the more decriptive the better) and which of the sites you want me to link to.