Any idea can be effective on fiverr actually. Here is some food for thought, and a couple of the common sense things that get overlooked about fiverr as a marketing platform:
1. Gig Extras. A good service provider can often scale production on his/her gig to higher levels and thereby jack up their overall gig value. Often this can be achieved without adding any real work to the project. A solid example of this can be found by searching Fiverr for whiteboard video creation services. Admittedly this is a specialized type of service, but it's also a very easily learned one. I make these whiteboard videos all the time just for fun, or for business projects or as outsourcing. I do not currently run any whiteboard video services on fiverr. I just know when I researched these gigs recently it very clearly illustrated how a Fiverr gig can become very profitable.
2. Automation Tasks - anything which can be web-based is easy to automate using iMacros or other bot solutions. That's why so many providers offer SEO type services, and scrapebox blasts. Using the right tools one could pretty easily create some recurring projects in their softwares, and then fulfilling a gig is simply a matter of plugging some information into a spreadsheet + turning your bot on. What might take a few hours to run as a project the first few times can be automated, simplified, adapted, and turned into a very successful gig.
For example as extras on your gig, you might try adding something else of value to the offer such as:
a) Will add a killer logo. $15 total gig price, and you could simply buy a $5 logo design gig to get the logo done.
b) Will add a 15 second whiteboard video with audio a logo and your slogan. $40 total gig value, and you could outsource the whiteboard video and logo for about $10 on Fiverr.
Maybe you play around with what to add to your gig as extras, or perhaps the pricing options, but actually all you need to do is get creative with what you are doing currently. However, I would look for some easily duplicatable projects to add some more gigs to my portfolio if I were you. Perhaps some of those GIRL holding a sign things can work. I bet a lot of girls will hold a sign if you just tell them they are pretty ... or you could split the profits with a pretty girl from your neighborhood. Or do some graphic stuff if you can ... a lot of those KILLER intro video things are just After Effects templates that people use, so it literally takes them about 1 minute to do the work to create that KILLER video intro.