"Internet for Image Searching" is a new, free online tutorial to help staff
and students in universities and colleges to find digital images for their
learning and teaching:
The emphasis of the tutorial is on finding copyright cleared images which
are available free; facilitating quick, hassle-free access to a vast range
of online photographs and other visual resources.
This tutorial has been created by TASI - the JISC Advisory Service for
digital media, and Intute as part of the Virtual Training Suite, with
funding from the Higher Education Academy/JISC Collaboration Initiative.
An image resource that may be particularly useful for engineers is the "CAL visual for construction image database", created by Loughborough University http://www.engsc.ac.uk/resources/calvisual/index.asp
Also available for Bioscientists is the "Centre for bioscience image bank" http://www.bioscience.heacademy.ac.uk/imagebank/
The tutorial will introduce you to many other image sites.
You may also find the TASI pages on "Finding Scientific Images" useful http://www.tasi.ac.uk/advice/using/finding_science.html