using theme images directly in header.php (url?)

hello, i want to use images that i have put in the theme-images folder as links directly in header.php. I want to use icons as link buttons directly in the header.php file.
what relative url do i use to find these files? it doesn’t seem to work if i just use images/image.png in the header file.

i hope this is not a totally stupid question, I am pretty new to wordpress…

/oscar, sweden