Yes, you can! Realestate.com.au offers what's called an 'Upgraded Listing'. Upgrades can give you a larger image, push you higher in search results and offer other benefits. Upgrades operate on a 30-day cycle and are an additional cost. Realestate.com.au upgrades are available from within your account - you'll find the 'Realestate.com.au Upgrades' button on the left-hand side once logged in.
More information on Upgrades is available here: http://sellingguide.realestate.com.au/advertising/
We recommend speaking to a staff member before purchasing an upgrade to ensure you have all the information you need to make an informed decision, before opening your wallet.