As you note, you didn't create the design -- you re-created it. Which is another way of saying you copied it [perhaps by freehand but, in any event, "as close as" you could]. Assuming the design is copyrightable [a good assumption] your copying of that design is copyright infringement. You should NOT use that design on an invitation and then offer that invitation for sale. Speak with your own copyright attorney, of course, and read a book or two about crafting [visit the link below]. Good luck.
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As close as you can is too close. Either it's a copy or a derivative, and either of those would be an infringement of the exclusive rights of the owner of the copyright to the original under 17 USC 106. Don't sell any of your infringing design until you get clearance from a copyright attorney, who will likely tell you you need to be as different as possible, not as close as possible.
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I you can probably glean there is no way for us to conduct a conclusive analysis in this forum, but as the others have noted what you described would be an infringement.
It may not be likely that you would be held accountable if your creation is substantially different even if you based it on that other design. But all that matters really is whether the copyright owner a) discovers your work and b) clearly considers it an infringement.
If you are seeking a more formal analysis you need to discuss with a lawyer in private and have that lawyer look everything over. But to repeat the other's comments, you cannot copy another's work and claim it as your own just because you yourself made the copy freehand.
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You are probably engaging in copyright infringement. Any work fixed in a tangible medium of expression is protected by copyright law. Even though you do not copy the exact images, you try to "recreate the design as close as I can". Such recreations constitute copying----you admit that you try to recreate "substantially similar" designs. The test for copyright infringement is whether the accused infringing design is "substantially similar". Someday very soon you are going to be sued for copyright infringement, and you will face damages of up to $150,000 for each invitation that you have willfully infringed.
You would be much better off developing your own original designs--then you own the copyrights and can stop worrying about getting sued.