The contents of cache/themes can be safely ignored at least from Sugar 6 onward.

Jens Jahnke · Jens Jahnke · commit d4467b7bcf75 · 2011-07-06T14:54:38.000+02:00
diff --git a/SugarCRM.gitignore b/SugarCRM.gitignore
@@ -14,6 +14,7 @@ cache/modules/*
 cache/pdf/*
 cache/smarty/cache/*
 cache/smarty/templates_c/*
+cache/themes/*
 cache/xml/*
 # Ignore some files and directories from the custom directory.
 custom/history/*
