Steve Milne sent me a copy, and a pdf, of his "Infinite Families of Exact Sums of Squares Formulas, Jacobi Elliptic Functions, Continued Fractions, and Schur Functions" which is an entire issue of The Ramanujan Journal: vol. 6, no. 1, March 2002. There is also a two-page preface by George Andrews. I admit, the main focus is dimension $4 n^2$ or $ 4 ( n^2 + n).$ But at 143 pages and 259 references, there might be something you like. Email me if you would like the pdf, it is not obvious to me that there was implied permission for me to post it on any websites.
Robin Chapman mentions the papers on odd numbers of squares by Shaun Cooper, some previews at
http://www.springerlink.com/content/w1w160424g78284l/
and this is the guy: http://www.massey.ac.nz/~wwiims/people/s.cooper/