Is clip art appropriate for a business letter?

Clip art is art work that is distributed on a computer CD.  Some clip art is made to use with business letters and presentations, such as graphs and percent ratios.  Also some logos are made with clip art.  If you use clip art on a business letter or presentation, make sure it is viewed as professional.  For example I do not recommend cartoon like clip art for business letters.

Clip art contains pictures, and it probably isn't good for a business letter

No. You can use it on an enclosure, such as a flyer, but it is not appropriate on a business letter.

No. The only time that it would be is if they asked for it to be inclosed