They said if I cite them it should be fine
Again, that can help but isn't necessarily true.
If you ended up in court and the ruling was against you the fact that you knowingly infringed upon iD's copyright (as shown by your citation) could result in higher damages being awarded than if you had naively done so. See also frob's response in another recent topic, citing similar rationale based on the concept of willful infringement.
As above, you may or may not be protected by Fair Use, but only a judge can decide that, and if it turns out you aren't protected it could actually be worse for you to have cited the source.
It's up to you whether or not you want to take the risk, but you should be able to find some freely available resources that don't carry the same risk; see OpenGameArt.org and Texture Warehouse for example -- you should be able to locate other similar resources with a little searching.