Alot of Yngwie solos,as an example,employ the repetition of a single note/chord,while he improvises over the top of it.The less melodic the background chord sequence,themore freedom and variations are possible.Melody is achieved in two ways,by the accompaniment or the soloist,sometimes both. Lead guitarists prefer simple accompaniment,allowing them to dictate pace,content,and melodic direction.One case where a lead may be handcuffed to a single scale or pattern is diminished,no other scale or pattern really works other than diminished with diminished,which is probably why,other than Yngwie,it's not widely used.To summarize,a "busy" accompaniment is generally not advisable.