Replying to Giving photo credit for informational website project

What's up guys, for one of my end of year reports for a course I'm doing at Uni (geology) I am making an informational website around the impact that the warming/melting cryosphere will have on skiing in terms of areal snow coverage, snowfall, avalanche risk etc. and I want to try and use some good skiing pictures for backgrounds on the website. There are tons of cool pictures on NS I could use but will copyrighting shit matter? the website has to be made public while they mark it but can then be closed, some of the pics I want to use from here are from members that haven't been active for at least 2 years, can I use them anyway?