The choice of either having an illustrative logo design solely depends on the type of business the logo design is intended for. For instance, it would be impractical for a consulting company or law firm to have an illustrative logo design as the face of their business as it would not reflect the company as well as a corporate iconic type. But then when is it suitable to have an illustration as a logo design, you ask? If your business is towards the creative side or even one which is geared towards children and teenagers, then it could do well for your brand. As mentioned, it is essential to identify the type of business you are involved in to determine the appropriateness of having an illustration as your logo design.
An illustration can do wonders both as a means of attracting your audience and distinguishing yourself from other basic logo designs. In terms of color combination, it would be appropriate to keep it at a minimum as too many colors might cloud your overall logo thereby affecting its impact on potential customers. Complementary colors are also perfect to bring out the core design of the illustration. Still on the topic of the importance of colors, occasionally having an illustration done in black and white or typical gray-scale can bring out the logo as well. I have included some samples of illustrative logo designs for your enjoyment as seen above.
The types of illustration used are also important. An emblem? A mascot? Or a caricature? They are all good but still it all boils down to the needs of your business. On a different note, most people usually dismiss this but choosing the right designer to do your illustrative logo is highly important as well. Always check the portfolio to see the quality of the illustrations. Do not be afraid to tell your designers what you want or exactly have in mind as this will make or break the final design. Provide samples or sketches you have as this will definitely aid in bringing your vision to reality.