use
Get-MailboxStatistics -Database "mailbox database" | Sort -Property DisplayName | ft DisplayName, @{expression={$_.totalitemsize.value.ToMB()};label="Mailbox Size(MB)"}, itemcount, lastlogontime, lastlogofftime,lastloggedonuseraccount
As a bonus it sorts by displayname
If you don't want to specify database name:
get-mailbox | get-mailboxstatistics | select-object DisplayName,TotalItemSize,StorageLimitStatus,LastLogonTime
Attachment type and size is an interesting question, I'll have to see if that possible without chugging through each message, if you do have to do it per message I'd say it's not worth the effort unless you are looking at some compliance issue (but then I'd say start creating transport rules)