The formatting of a block quote depends on the style guide to which you adhere. For example, this Google Doc Template is for an MLA Style Research Paper in which block quotes are indented an inch from the left hand margin (see MLA Formatting Quotations). I know in college I was taught to indent from both the right and left hand sides and single space the block quote.
The Chicago Manual of Style says block quotes should be indented a half inch and single spaced, while APA Formatting maintains double spacing at a half inch margin. For visual effect, of course, you can change the typography, though that would not be adhering to any 'academic' style guide I'm familiar with.
Robert Bringhurst's The Elements of Typographic Style suggests the use of elastic leading before and after block quotations:
2.3.3 Add extra lead before and after block quotations.
“But if the leading within the block quotation differs from the leading of the
main text, these blanks before and after the quotation must be
elastic. They afford the only opportunity for bringing the text back
into phase.” (41)