When I was starting off on my own to setup aside as a design studio, I was never too sure whether to restrict my portfolio to certain deliverables explicitly or to be open to all kinds of design work. In the recent years I have come to realize that it is better to take on design engagements that challenge you creatively rather than taking on something just to earn some bread and butter.
While some design sub-professions [ like web development for example ] require specialized skill and training before a designer can offer such services on their portfolio, the common thread among all design professions is the requirement of creativity. So I do web-design but not web development [ atleas not on a large scale – I’ve built my own websites and constantly tweak my blogs for better performance ].
At the same time, one should not pass up an opportunity to test one’s capabilities in new design areas. But do inform the client. When a client comes to you with a design requirement, as a designer or service provider, it is absolutely essential to inform the client whether you are fully capable of delivering upto his/her expectations or whether you are willing to do it on an experimental basis. An informed client is always a happier one and even if you lose the work, the client will remember you for his next requirement that fits your profile. And if the client does agree to work with you, you’ll have a fantastic time working on the design engagement because you’re working with someone who has faith in you as a designer!