There is an awful lot of country to cover.
Ride up:-
How about turning west through Dumfries and then up the A713 to Ayr. This will take you through Galloway which is beautiful.
From Ayr you could either ride the coast road, over the Erskine Bridge and up the A82 then A85 to Perth (which I agree is a good base) although this would make it a long days riding as although they are A roads they aren't A roads as you know them, well maybe as you stay in the lakes. They are scenic but can be slow. About 370 miles and could be 7 or 8 hours in the saddle. But what a ride! The alternative would be to curtail the scenic route at Ayr and take the A77/M77/M8/A80/M80/M9/A9 directly to Perth which would be much quicker, probably around 6 hours in the saddle. Still some nice scenery but dual carriageway boredom.
Loop option 1
A85 west from Perth either to Oban and then north or turn north earlier at Tyndrum up the A82 through Glencoe and on to Fort William. From there ride the Great Glen past Loch Ness to Inverness (recently awarded city status) and then back to Perth down the A9. Once again this is a long day, 280 miles without including Oban and maybe 7 hours. If you cut out the Inverness part of the loop you can come back through "Monarch of the Glen" country and reduce the day to around 200 miles and about 5 hours riding time.
Loop option 2
I suggest heading east to Dundee and then south through the Kingdom of Fife and then crossing the The River Forth to have a look at Edinburgh before completing the loop back to Perth.
There are plenty of Fifers on here who can give routes through this area as I don't know it very well.
Monday head back south past Dunfirmline take the A720 Edinburgh ring road and then pick up the A7 to continue south through the borders with famous towns such as Selkirk and Hawick on your route all the way to Carlisle and on to home.
As well as fuel/meal stops if you're photographers you will want to make lots of stops as some of the scenery is simply amazing.
You will also need to prepare for cold weather at Easter. You could easily find temperatures close to zero especially at higher levels such as Rannoch Moor which is over 1100 feet above sea level.
Buchaille Etive Mhor NW of Rannoch Moor, you would ride pass this on Loop 1.
