A few nice business license images I found:
Business-Envelope_73295-480x360
Image by Public Domain Photos
Free Photos – White envelopes for letters / Business Envelope
More photos and details about possible copyright or licensing restrictions here:
public-photo.net/office-supplies/business-envelope/
Full Size Up to 3072 x 2304 pixels
Information Regarding Copyright: public-photo.net/copyright/
